Guitar Theory (Idiot's Guides) by David Hodge

Idiot's Guides: Guitar Theory is music theory for guitar and other fretboard instruments. Beginning with very simple and clear explanations, the book defines notes, their names, relationships, and guitar tablature and then explains rhythm, keeping time, and strumming. The book then goes into depth on the major scale and the four basic chords, to make guitar theory very clear and keep it easy, before going into all the chords and scales. The last part of the book covers playing solo and with others. There is more than an hour of listen- and follow-along audio files online with all of the music in the book and more.