I have 3 of the 4 books you mention (Moon, Insight, and Sluder). If you are spending all or most of your time on AC, I think the general Belize guide books aren't worth the money. Lan Sluder's is good, but outdated; still interesting though.

IMO, the BEST source of information for travelers to San Pedro and Ambergris Caye is THIS WEB SITE. More information, current, and if you browse the links, you can find most anything you might want to know -- with illustrations and maps, as well as lots of advice and personal feedback from other travelers and residents. THANK YOU MARTY!