I haven't played bass for about 4 years and recently rekindled my relationship with making music, bought a bass guitar and joined a band. I was never the best or most creative musician anyway.
This book's purpose is to 'train your fingers', and I think it does a great job at making it not a chore, but a fun exercise. Everything it makes you play sounds cool and it encourages you to experiment and go your own pace. It starts you off with chromatic walking lines that I could never have imagined, but following the instructions it just makes sense to me and makes me feel smart.
I've only done the first 5 lessons so far, but I like it very much and I'd recommend this to anyone who has a little experience playing and reading music, or someone who's just starting out and can see a teacher once in a while to review and help with progressing through the book.