What level are you at? I think Jem7vwh's posts on this forum are excellent, and you might like the following list from Steve Vai:
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While a thorough understanding of all these basic theory points is very useful, it's not a necessity, because music is an art form. No one has the right to say, "Our noise is better than their noise". It's totally relative. However, if you are a connoisseur of fine theory, here's a list of some books that I found very helpful when I was a student:
Ted Greene's "Chord Chemistry" **Hamand's note:
Eric Johnson also raves about this book**
(Dale Zdenek, dist. by Columbia Pictures Pub., 15800 NW 48th Ave, Miami FL 33014).
All of the Bill Levitt Berklee series books
(Berklee Guitar Series, dist. by G. Schirmer, 886 3rd Ave., New York NY 10022)
A good fake book.
Nicholas Slonimsky's "Thesaurus Of Scales And Melodic Patterns"
(dist. by G. Schirmer, 886 3rd Ave., New York NY 10022)
"Rhythms 1 & 2" by Gary Chaffe.
Violin or saxophone books for reading practice.
Gardner Reed's "Music Notation"
(dist. by Crescendo, 48-50 Melrose St., Boston, MA)
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http://www.vai.com/LittleBlackDots/MLS_01.html
It also depends on what your goals are. Who do you like listening to? Is the amount of theory even necessary for what you want to do? Whether you like Steve's music or not, there's no doubting his theoretical knowledge, hence me providing the above list. I also recommend (via Satch's recommendation) "Joe Pass Guitar Chords" as this will expand your ability to "invent stuff."
Frank Gambale's improvisation books are excellent. Anything by Troy Stetina is always good. Like I said, what are you setting your sights on?
