I have only lightly dipped into Crusade history, but the portrait the author paints seems inaccurate. Please, any insights or corrections are welcome.
http://www.firstthings.com/article/2009/06/inventing-the-crusades
that's actually a review of a book by Jonathan Riley-Smith. The book's ok. It attempts to show that the "Crusades" in the Islamic world passed out of memory until 19th-century colonialists showed up. Recent scholarship in Arabic has shown that that's just not the case though.