Oh frabjous day! At last, a well researched, sane, balanced book about the Crusader Kingdom of Jerusalem... which is also a pleasure to read!
Bartlett's DOWNFALL OF THE CRUSADER KINGDOM, I presume, was written to present the true story mangled by Ridley Scott in KINGDOM OF HEAVEN. It's well written, comprehensive, and far more accessible than either Malcolm Barber's or Bernard Hamilton's accounts of the same period. Bartlett writes with an eye to the bigger themes, the grandeur of the stories being played out here, rather than slogging through minute details. While details can be helpful (and details there are aplenty), it's sometimes more useful to pull back and see the bigger picture.
On the other hand, while Bartlett gains one's respect for his careful and evenhanded treatment of the different characters and factions involved in the history, his research isn't quite up to date and I would disagree with some of his evaluations. For example, he puts the blame for Saladin's aggression against Jerusalem on Reynald of Chatillon for attacking Muslim caravans. Though time-honoured, this theory fails to take into account the fact that Saladin subscribed to an ideology of jihad and was already preparing to invade the kingdom when Reynald organised his 1187 raid. I don't agree with trucebreaking as a military tactic, but more recent scholars like Bernard Hamilton have argued persuasively that Reynald showed good strategic thinking in his raids, which may have infuriated the Muslim world but certainly didn't provoke them to take any action they wouldn't have taken anyway.
Similarly, Bartlett makes much of the ill effects of the warring nobility on the kingdom's chances, arguing that Baldwin IV's reign saw the nobles becoming too powerful for the kingdom's good. I'm not so convinced. Baldwin IV was able to lead them well enough when his health was up to it, and the major problem seems to have been not that the nobles were too strong but that Guy of Lusignan was too weak and too controversial to lead them.
There were other quibbles I had, but those are the main ones. Overall, this was a splendid introduction to a truly amazing and spectacular period of history. If your previous exposure to the fall of Jerusalem in 1187 had been limited to novels like Welch's KNIGHT CRUSADER or Haggard's THE BRETHREN, or (alas) that Ridley Scott movie, Bartlett's DOWNFALL OF THE CRUSADER KINGDOM is a fantastic way to delve into the history behind.