My teaching method here at Modern Blues Harmonica, which utilizes videos and tab sheets in combination, is the best way I know for communicating the THREE ESSENTIALS OF BLUES HARMONICA, none of which can be adequately represented using standard musical notation:
1) TONE: the unique sound that a player actually produces, including the "dirt" around the edges of notes, various sorts of vibrato and tremolo, a frequency range (a thin or thick tone) determined by the shape of the mouth; etc.
2) MICROTONAL INFLECTIONS: the blues pitches BETWEEN the notes on the piano and the frets of a guitar. Quarter-tones. Rising and falling pitch-edges on notes.
3) GROOVE, which includes syncopation or "swing" and a range of rhythmic subtleties that add forward motion and other kinds of energy to blues rhythms and melodies. (My tabbing system is particularly concerned with drawing your attention to these subtleties.)
Let me be blunt: it is IMPOSSIBLE to learn blues harmonica from books alone. Not the real stuff. It can't be done.
But books--instructional books, standard sheet music, and various forms of tablature other than my own--do have their place. And I'd encourage all serious students of the blues harmonica to supplement the materials I'm offering on this website with at least a couple of books by other people. I read sheet music very poorly, but more than twenty years ago I managed to create an arrangement of Scott Joplin's ragtime classic, "The Entertainer," working my way slowly through the sheet music, and it remains a treasured song in my repertoire. Although I believe that my tab system is superior to tabs that give you little or no sense of note duration and note placement relative to the bar lines, those other tabs can be useful; they can help you locate familiar folk melodies and Christmas carols on your harmonica, for example, and thus expand your repertoire. They can save you some time. They can broaden your approach.
If you're in the market for HARMONICA SHEET MUSIC, you might want to check out the offerings at SHEET MUSIC PLUS. They've got more than 450 items in their harmonica catalogue:
Harmonica music at Sheet Music Plus