There used to be quite a few blues songbooks and instructional books, but apart from the fall off in demand for books with the growth of Internet sites, I doubt that there was ever a great demand for blues songbooks because most blues songs follow the standard 12 bar blues chord sequence. Those just wanting the chords to the songs can easily work them out themselves once they’ve landed in the right key (by trial and error), but those who want to play particular arrangements, or were thrown by recordings in open tunings, rather than simply improvise their own accompaniments could seek out some excellent books with tablature, as mentioned above, by the likes of Stefan Grossman, Woody Mann and others.