The LPI exams evolve following the advances in technology, albeit at a slower pace, so it depends a lot on when the book in question was written/published and if it's still up to date. I've been leading a set of workshops in preparation to the LPIC-1 certification exams and have used primarily the following:
to get an idea of required knowledge and a starting point. Of great importance are the addendum parts listed at the top of the requirements since they indicate what will be covered/discontinued in the actual exams. If you want to stay up to date on the Revision (2.5 y) and redo (5 y) cycle, have a look at this page
Besides using the LPI wiki I used the Linux Professional Institute (LPI) exam prep from IBM developerWorks
extensively and Google for the parts that were missing, keeping the LPI objectives in mind.
Most of the guys attending the workshops I mentioned before, have passed the 101 exam with ease in the last month. Hope this helps.