This best selling book, 100 Ultimate Blues Riffs by Andrew Gordon is an exhaustive guide to some of the best musical phrases that make up blues piano/keyboard playing. There are five sections broken down into:

The 12 bar Blues progression and the Blues scale are explained. There are two completed songs at the back of the book that shows how to combine many of the riffs to form a song.
The London College of Music in the U.K. is currently using examples from the "100 Ultimate Blues Riffs for Piano/Keyboards"  in their jazz program as part of their recommended learning materials from grade 3 through grade 8.