another book I like even better than Ned's is "Mastering Mountain Bike Skills: techniques to excell in all riding styles " by Brian Lopes and Lee McCormack.
This book rocks! Shows great illustrations and is much more current(ie 2005 vs Ned's 1999).. Great book! You want it, check it out at a book store and you will agree.. .
I have bunches of different books and this one stands alone..