Search previous postings on this topic. This topic has been discussed at least twice in the time I've been here. There are no books specifically on off road suspension design that I'm aware of, but there a couple good ones on road race stuff and all of the same principles apply. Just understand that their goals are different, so the geometry you choose probably won't be the geometry they would choose.
"It only seems kinky the first time"
-- Bumpersticker seen in Lost Wages
Drive to Win: The Essential Guide to Race Driving by Carroll Smith
Carroll Smith's Nuts, Bolts and Fasteners by Carroll Smith
How to Make Your Car Handle by Fred Puhn
Chassis Engineering/Chassis Design, Building & Tuning for High Performance Handling by Herb Adams
Competiton Car Suspension: Design, Construction, Tuning by Allan Staniforth