Our findings are that you can still use the cheap Official PrepTest books--the only LSAT books Zen of 180 recommends--from the "before" 1998-2007 LSATs and still get appropriate practice on logical reasoning for the newest LSATs from "after" the June 2007 LSAT redesign.
Lots of people worry about whether they have to spring for the brand spanking new, $8-a-pop PrepTests; our analysis of the Zen task strands show that the newest books are not necessary to get accurate scale scores for logical reasoning sections. While analytical reasoning has been made indisputably harder with more hybrid games and reading comprehension stole a question from AR and added comparative passages in 2007, the logical reasoning sections have remained relatively unchanged.
As you can see from the graph, the relative importance of each task strand to the others has remained the same except for the bottom two, identify similar logic and analyze different viewpoints, switching places. The small drifts in point distribution are not significant enough to warrant the exclusion of the older LSATs from your study.
However, there have been some significant point distribution changes within individual strands, as opposed to between strands. We'll be introducing each of the 22 different tasks--like we did with criticizing evidence--found in logical reasoning sections across February, and discuss how to identify them and how they have changed across modern LSATs.
If you don't know the difference between Zen task standards and Zen task strands, one of our previous clients offered a simple introduction.