In addition to the oddest cover design ever, 30-Day Guitar Workout offers great exercises and has improved my playing.
Jody Fisher's 30-Day Guitar Workout runs me through a series of scales, chords, pick and play styles. By using this guides' simple warm-ups, and then daily exercises, as part of my practice regimen I've greatly improved my technical skill and my understanding of the fretboard.
I am lazy and didn't really want to think about good repetitive patterns to play, or exercises that'd help me learn to be a better guitarist. I realized I had learned to play a few songs on the guitar, but not to play the instrument itself. Regular work with this workbook has gone a long way to correcting that. I still play the same 4 or 5 songs over and over, now I just do it better.
I have not tried the DVD that came with the book, I tend not to find them all that helpful. I see there is a Kindle edition available as well, I am not sure how well that'd work for practicing music.