Has anyone checked out the Mick Goodrick book entitled "The Advancing Guitarist"? It's excellent and is almost entirely applicable to electric bass playing. One idea he presents is playing some solos on one string which really forces you out of "positional playing". I also picked up a small book called "Single String Solos for Electric Bass" by Bruce Arnold. Both books are very cheap and are available at amazon. I've found that these are really forcing me to break out of any old patterns / licks that I've established and I feel that I'm able to move around the neck with a lot more freedom. Has anyone else checked these books out?

Haven't checked out either, but I can imagine that the Goodrick book is excellent. The man is a fine guitarist (check out his 1979 ECM date In Pas(s)ing sometime) and one of the premier educators on the instrument.