The following article is based on the Watchtower study guide, 'What Does The Bible Really Teach?'
If you're interested in the Bible, read this article first before you read the book or study with the Witnesses. JW's are nice people. They are very friendly and sincere. Many things they teach are very attractive. But they are also very wrong. They have been misled and zealously promote Watchtower doctrines that are not supported by the Bible. Here are some reasons to be cautious.
They don't allow blood transfusions to save a life.
They've caused much emotional pain and suffering because they believe there are only two choices, - God's organization, JW.ORG, and Satan's organization, - everyone else. This has destroyed millions of families and close friendships needlessly in the name of God. See Isolation From The World
In addition. according to psychologists, their doctrines can lead to depression, anxiety, stress, anger, and mental illness. As former JW's we noticed this tendency as well based on personal experiences.
The Watchtower publishes a book called What Does The Bible Really Teach? It is a study guide to help you understand how they interpret the Bible.
If you decide to read this Watchtower publication, beware. It looks like a very innocent publication that exposes 'the truth', but in fact if you know what to look for, you'll see that it's filled with false assumptions and incorrect information.
The best way to convince yourself that the Watchtower doesn't have the truth is to read their publication about what the Bible really teaches. Carefully read this entire article first. Then carefully read what the Watchtower says. As you read the book, 'What Does The Bible Really Teach', look for evidence of misleading information that's falsely presented as 'the truth'.
Their style of writing, graphics, and convincing presentation of Bible 'truths' leads people to believe they've stumbled upon the best religion in the world and their former religious teachers have lied to them because the entire world is under Satan's control except for JW.ORG. 
The Watchtower uses the Bible to 'prove' what they say. But they don't use the organization to prove what the Bible says. What this means is their publications lead you to believe in things that are not true at all. If you carefully read all the articles on this site, you'll see that what they teach is not from the Bible. They've added to what the Bible says and have interpreted it incorrectly.
They make you believe they have 'the truth' because quotes from the Bible are everywhere. However quoting Bible scriptures doesn't 'prove' anything. The very same scriptures could be used to 'prove' totally different doctrines.
Some say the Watchtower invented 'the truth' based on the personal beliefs of their founder, Charles Taze Russell. Leaders who followed Russell added their own 'truths' as the years went by. These 'truths' are not truths at all.
WT leaders have looked everywhere for documentation to support what they believe. Notice what the very first issue of the Watchtower said in 1879.
The July 1879 Watchtower said this. "We should learn to love and value truth for its own sake; to respect and honor it by owning and acknowledging it wherever we find it and by whomsoever presented. A truth presented by Satan himself is just as true as a truth stated by God. ... Accept truth wherever you find it, no matter what it contradicts. " Watchtower, July 1879, p 8, Headline: "What Is Truth?".
Thus they teach many doctrines that are not based on what the Bible says. That doesn't stop them from using the Bible. All they do is quote a Bible verse and then explain what the Bible 'really' teaches. In other words, this is what the Bible says, but this is what it 'really' means.
Based on years of experience inside the organization, this is what Witnesses will say to new people who are studying with them.
WT Bible studies will begin innocently and quickly ramp up. As soon as they have you saying 'yes' to truthful statements, they will have you saying 'yes' to things that are not true at all. It won't be noticeable, no matter how intelligent you are, unless you stay alert and know what to look for.
As you read their literature and study 'the Bible' with them, they will soon begin using the words 'obey' and 'disobey'. You will learn how important it is to love Jehovah by being obedient. Once they have you believing you must be obedient to Jehovah, they will convince you that obeying them is the logical thing to do. e.g. consider their baptism vows and the following question posed by JW.ORG.
The Watchtower says this, ' By word or action, may we never challenge the channel of communication that Jehovah is using today. ... we should cherish our privilege to cooperate ... and should we not strive to be obedient and submissive to those taking the lead in our local congregation?' WT, Nov 15, 2009, Article: 'Treasure Your Place in the Congregation', par 5.
To see a list of Watchtower rules that must be obeyed, refer to the secret book for Elder's only, Shepherd the Flock of God
In addition to obeying them, they will lead you to believe that everyone who disagrees with 'the truth' as they interpret it, is God's enemy. Everyone outside the organization is painted with the same brush. They are part of Satan's 'wicked system of things'. 
Anyone who does not obey the Watchtower is thought to be influenced by the devil's wicked world. This is a lie. You know it is. Good people are everywhere, - inside and outside the Watchtower organization. God is in every religion. The potential to make mistakes and sin exists in all religions as well. Everyone is doing their best, but none are perfect, - not even JW.ORG. 
They will show you scriptures that say ' Satan, who is the god of this world, has blinded the minds of those who don't believe.' 2 Cor 4:4 and 'Satan himself masquerades as an angel of light.' 2 Cor 11:14 and 'Be self-controlled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour.' 1 Peter 5:8. They use these scriptures to prove that the entire world is in spiritual darkness and controlled by Satan. Therefore we should never question the Watchtower or rebel against the organization. There's no where else to go. Trusted friends and relatives who have stuck with you through good and bad times, are now on a mission to deceive you. Trust us instead because those who reject us are influenced by Satan's wicked world. These too are lies. You know they are.
Notice that the above scriptures could be easily used to 'prove' that the Watchtower is our enemy and controlled by Satan. Quoting Bible scriptures does not prove that only one religion has 'the truth' and others don't.
Be alert when you read religious interpretations of what the Bible 'really' teaches. The Bible can be interpreted in many different ways and it can be used to support virtually any belief. Quoting from the Bible doesn't 'prove' anything. It just offers a different viewpoint.
Rainbows can teach us a lot about religious truths. Watch this educational video about What Rainbows Can Teach Us About God
Learn how the doctrine of Satan and wicked spirits is used as a fear tactic to control millions of JW's
Through mental pictures, colorful illustrations, false logic, questions that lead you down the wrong path, and clever wordology, they will take control of your mind if you don't notice what they're doing.
Their literature will train you on a subconscious level to obey, fear, and trust only them because they are the only ones with 'the truth'. They are the only religion that God approves of because they use God's 'real' name, 'Jehovah', etc., ...
At the same time they will train you on a subconscious level to distrust and turn your mind off when you hear any opposing viewpoints, - even it's coming from people you've trusted your entire life.
The Watchtower warns new recruits not to listen to family members and friends. Once you decide to join the JW's, there's very little your family and friends can say to convince you to leave. Much like the 'Borg' on Star Trek, you now belong to the collective. You share one mind. The organization comes first and you will defend it at all costs against 'God's enemy', - the entire world 'controlled by Satan'.
Notice what the Watchtower says, 'Satan’s influence may be seen when friends, relatives, or others oppose your efforts to study the Bible and apply what you learn. ... The Devil can use subtle means to mislead you and lure you away from a godly way of life. ... He says that when you are faced with trials or temptations, you will stop serving God. How can you answer his challenge and prove your integrity to God, as Job did?' WT, 'What Does The Bible Really Teach', 2005, pp 120-121, par 16
To be fair, the footnote below the above paragraph on page 120 says, 'This does not mean that those who oppose you are personally controlled by Satan. But Satan is the god of this system of things, and the whole world is in his power. (2 Corinthians 4:4; 1 John 5:19) So we can expect that living a godly life will be an unpopular course, and some will oppose you.'
It's easy to get sucked into a cult. Once you belong to JW.ORG, it's very difficult to escape. You can leave physically, but they will have your mind. Through disfellowshipping and shunning they will intimidate and manipulate you into staying.
If you decide to disobey them and leave, they will continue to control your thoughts.
Without help from the outside world (that you no longer trust), you will feel compelled to go back to the Watchtower and you won't know why.
(HINT: If you're a JW who disagrees with the Watchtower and still believes they have the truth, read the last sentence a few times. They got your mind. They've beat it into your brain over and over again that you have no where else to go. That's a lie. It's not true but a little voice in the back of your mind says, 'yes they do have the truth. I just don't know why I believe that'. Read the following articles with an 'open' mind and take your power back.
1. The book 'What Does The Bible Really Teach?' is 224 pages long. It is jam packed with loads of false assumptions that appear truthful to unsuspecting readers. e.g. How many false assumptions can you find in the following three paragraph alone?
'Does your religion agree with what the Bible teaches about the dead? Most do not. Why? Because their teachings have been influenced by Satan. He uses false religion to get people to believe that after their body dies, they will continue to live in the spirit realm. This is a lie that Satan combines with other lies to turn people away from Jehovah God.' WT, Book: 'What Does The Bible Really Teach?', 2005, Page 64, par 16
'Knowing the truth about the dead protects you from being misled by religious lies. It also helps you to understand other Bible teachings. For example, when you realize that people do not pass on to the spirit realm at death, the promise of everlasting life on a paradise earth takes on real meaning for you.' WT, Book: 'What Does The Bible Really Teach?', 2005, Page 65, par 19
'The Bible teaches that God will soon bring an end to this wicked system of things and will replace it with a righteous new world under the rulership of his Kingdom. (2 Peter 3:9, 13) What a marvelous world that will be! And in that righteous new system, there will be only one religion, one true form of worship. Is it not the course of wisdom for you to take the necessary steps to come into association with true worshipers right now?' WT, Book: 'What Does The Bible Really Teach?', 2005, Page 153, par 20
Take a look at a few examples of how they've altered the meaning of what the Bible says.
In the Watchtower religion, their literature is the primary source of information. The Bible is merely a reference book or tool that is exploited to promote their false doctrines.
If you want to understand the Bible, make it your primary source of information, - not religious magazines and books that 'explain' what the 'really' teaches. Agree to disagree with people and religions who have opinions as to what the Bible 'really' means. Never rely on any imperfect human religion as the source of truth. The Watchtower has admitted on rare occasions that they can make mistakes and have no divine inspiration. This means that some or all of what they teach today could be incorrect.
Read the Bible if you want to understand it, - even if it's only for a few minutes each day. Then as you consider various translations and interpretations from many sources, pray to God for wisdom and understanding.
If you're curious as to what the Watchtower teaches, go to the official website of JW's and search for the book, 'What Does The Bible Really Teach'. Analyze each sentence. Observe the words and mental suggestions often posed as questions. Don't be misled by quotes from the Bible. Anyone can use the Bible to prove anything. Stay alert and watch out for truthful looking concepts that are not true at all.
We avoid reading Watchtower literature unless we need specific information for an article. Unless you're extremely careful, Watchtower wordology will mess with your mind. So many members have told us the same thing. They see what the literature has done to their brain, but even decades later, it's hard to snap out of it and live a normal life.
As you read Watchtower publications be on the look out for false assumptions and twisted interpretations of the Bible. By quoting Bible verses without regard for what the Bible really says, the Watchtower has convinced JW's they have the authority of God and must be obeyed.
JW's say everyone must be 'teachable'. i.e. they must believe everything the Watchtower says, whether it makes sense or not. Critical thinking and asking tough questions is not allowed. However being 'teachable' is not the right word for what the Watchtower requires.