That book, and Philip K. Dick's "Man In A High Castle" got me interested in the subject of AH. That being said, it involved an interesting and not commonly encountered premise (possible conquest of Europe by Mesoamericans with the POD in XVth century, even though rather unlikely - especially since any crusade of a magnitude described in the book, no matter how devastating on the victors and losers alike, would leave Europe with generations of battle-hardened warriors with not much to do - think post-Reconquista Spain, and the places these Spaniards, considered the finest soldiers in Europe at the time, ended up in), and the outcome that actually for once had characters play god and succeed.