Here are some books that we strongly recommend:

1001 Guitar Tips and Tricks 

Guitar for Dummies (For Dummies) 

The "First Stage" Guitar Book - Learn How To Play
Guitar Easily & Quickly! 

Basic Instructor Guitar 

80S & '90s Rock : Melody Line, Chords and Lyrics
for Keyboard, Guitar, Vocal (Paperback Songs) 

Guitar Player (Magazine)

Super Sight-Reading Secrets: An Innovative,
Step-By-Step Program for Musical Keyboard
Players of All Levels

Piano for Dummies (For Dummies)

Keyboard (Magazine)