Bass Grooves (Book on Learning to Play Bass Guitar)
I have quite a few bass tutorial books and Bass Grooves by Ed Friedland is by far my favorite. I strongly recommend it to anyone who is who wants to learn how to play bass guitar.
What I like most about it is that it focuses on the importance of timing and how to play different types of rhythms. This focus (and the helpful information on how to count different types of rhythms) has not only helped my bass guitar playing but it's really helped my musicianship in general.
The importance of timing cannot be overstated when it comes to musicianship especially because so many people overlook it. There's a tendency to think it's all about the chords and/or notes but really if you're not playing with a good feel (or "groove") it's going to sound like crap no matter what chords or notes you're playing.
I find that too many music tutorial books (and I have a ton) sort of skip out when it comes to timing. Even the books I have on drumming don't spend enough time on timing and how to count different types of rhythms.
For example; I have a drum book that mentions the common count for straight 16th notes (1-e-and-ah...) but which then introduces triplets with no mention on how to count them. This is an absurd oversight.
But Bass Grooves goes into every different type of rhythm that you are likely to play (including 16th note triplets) and teaches you how to feel the groove internally so that you can play in time.
Of course there's more to the book then just the timing instruction, there's also some great examples of many different styles of bass guitar playing (with tabs, a CD to listen to, and thorough instruction.) It doesn't really go in-depth into any one particular style, but it introduces a lot of them.
If you're looking into learning to play bass then I think it would be wise to start with this book and once you've really mastered it then look for a book on whatever kind of style you are most interested in.
I really like the stuff on timing so much that I almost want to recommend this book to anyone who feels they have any kind of issues with rhythm even if they don't want to learn to play bass.
And that leads me to one last thing; Rhythm is a skill like any other. You can significantly improve your sense of rhythm with practice. I did a post on "becoming a drum machine" last year that goes into some details on some practices you can get started with now (this is good practice regardless of what instrument or style of music you play.)
Another good basic rhythm practice is "making the metronome disappear."