Well my exit journey started with reading both of Ray Franz' books (Crisis of Conscience and In Search of Christian Freedom). However, I have to emphasize that, the only reason I was even willing to pick up the books was that I had been out of the organization (disfellowshipped) for nearly two years. So essentially I had a good "drying out" period. Otherwise I never would've read them.
The line of reasoning that finally got me out was basically the same one Don Cameron uses in "Captives of a Concept", although I didn't read that book until much later. In short, it goes like this:
The most important doctrine of Jehovah's Witnesses is that their organization was selected by Jesus in 1919 to be his "channel of communication" in fulfillment of Matthew 24:45. If this doctrine is false, then all other teachings of the Watchtower are invalid and don't even need to be considered. In order for the Watchtower to have passed Jesus' inspection and receive his approval, they had to have been teaching the "right things" at the right "time."
Once you've established this, you simply have to examine what was being taught by the organization at the time when Jesus supposedly made his inspection (1914-1919) and ask yourself, "Does it makes sense that Jesus would have selected them based on these teachings?"
If you make this examination, what you'll find is virtually everything that was taught during that time period is now considered to be "old light," which is a fancy way of saying FALSE. So ask yourself, if the majority of the Witnesses' teachings were false and later had to be altered, how can you say that Jesus was pleased with them and gave his approval? In addition, it was about that time that "The Finished Mystery" was published, which is chock full of nonsensical, downright hilarious scriptural interpretations that, if made public today, would cause the organization no end of embarrassment.
Yes it's true....for all the "apostate" information I was reading, the final nail in the coffin, the moment when it finally dawned on me that this was not God's organization, came from reading the organization's own literature.
Also the doctrinal changes are a big one. The easiest one to point out is their interpretation of Romans 13:1, the superior authorities. In Russell's time, they correctly interpreted it as referring to earthly governments. Rutherford comes along and says "Oh no that's a teaching of evil Christendom; the superior authorities are really Jehovah God and his Christ." And then after Rutherford's death it gets changed back to the original (and correct) interpretation. This is a case where the whole "Oh but the light gets brighter!" line of reasoning totally falls apart.
"But the path of the righteous ones is like the bright light that gets cappriciously switched on and off by a group of senile men in Brooklyn, until you die of old age with unfulfilled hopes." Proverbs 4:18 (NWT)