"The Tiananmen Papers" surfaced with a big splash in January -- even the new U.S. president has said he will read them. The overall quality of the reports contained in this thick volume has been judged by a number of China scholars and intelligence experts to fall within the realm of believability, though University of Michigan China scholar Ken Lieberthal was quick to point out that such leaks tend to be edited in a way that is favorable to the political cause of the leaker. The plausibility of the Papers is high because there is little that is new, and what is familiar can be corroborated from other sources.
The Papers show that Li Peng was in favor of the crackdown and Zhao Ziyang opposed it, something that everyone on the square knew in 1989. The book also shows that Deng Xiaoping isn't as bad as we thought he was; he had doubts about calling in the troops and wanted to avoid bloodshed. We also learn that Deng, widely viewed in the West as a ruthless tyrant, was still interested in promoting reform and slightly annoyed that Zhao was credited as the engine of reform by those outside the party.
This is moderately interesting stuff, but it doesn't bear close analysis because of a couple of fudge factors, one being the packaging, the other the sourcing.