I generally run my students through the 3 volume set of books from Alfred Publishing, "Beginning Electric Bass", "Intermediate Electric Bass", and "Mastering Electric Bass".
Hal Leonard's book, "Electric Bass Composite" by Dan Dean is also pretty good.
Musician's Institute has some worthy bass books too, like "Music Reading For Bass" and "Grooves For Electric Bass".
In any event, it's a good idea to augment whatever you're doing with other materials, perhaps style or artist specific just to keep things varied and interesting. Blues with Mel Bay's "Complete Blues Bass Book" for example, or rock with the "Bass White Pages". Hal Leonard also has "Bass Play Along" books with cds in a variety of styles (I think there's 7 of them), plus a generalized "Rock Bass Method".
Peace, Mooh.