The second book starts with rhythm studies to add rhythmic variety to your
lines (the first book focusses solely on quarter note lines), then moves into
additional harmonic possibilities, touching on modal tunes and playing
'outside'. It also ends with standards, plus three 'mystery tunes' that you
work out by ear (a likely scenario for bass players at jams).
I like these books. The first has helped solidify ideas I had from various
other sources (haven't made it far into the second book, though). If you work
through it, I think you will have a firm foundation in walking. Plus, it'll
help your reading (something that I hadn't done before much).
BTW, Ed has mentioned Paul Chambers as a listening source on another email
list. I began transcribing the line from 'Oleo' with Miles Davis (um, on one
of the Workin', Relaxin', Steamin', Cookin' discs - very fast, but everyone
but the bass and the soloist lays out during the A parts) and the things that
Ed teaches in the first book are all in there! Quite enlightening.
Hope this helps,
Joel