Just the thing for preparing for a wedding: recommendations for books on the Crusades.
Sir Steven Runciman's Crusade opus.
What Were the Crusades? by Jonathan Riley-Smith. I got this for Heather in 2007. Hers is the brain to pick about it.
The Crusades: A Short History, by Jonathan Riley-Smith.
Atlas of the Crusades, edited by Jonathan Riley-Smith.
Byzantium and the Crusades by Jonathan Harris.
Brief explanation: Sir Steven's classic is a little creaky, but still quite respected. He also tends to be more sympathetic to the Byzantines (especially) and the Muslims. But not a disqualifying bias by any means.
Riley-Smith is probably the best Crusades historian in the field today. Also, he takes a broader view of crusading, looking at wars outside of the Levant. The Atlas is fantastic in showing the breadth of the conflicts. He makes a pretty solid argument that elements of crusading continued into the late 17th Century, with the wars against the Ottomans. Also, he tries to understand the Crusaders at their own level, and not from (presumed) perfect moral hindsight.
Harris' work is a solid survey of the clash, first of worldviews, then of swords, between Eastern and Western Christians, as a result of crusading.