Logical reasoning, is a section where you have to understand arguments. Many people have said that formal logic can assist you in the logical reasoning portion as much as the logical games. I beg to differ.
firstly, formal logic is presented in a manner which is dissimilar to LSAT Arguments. Sure when you break the Argument down to its most fundamental/rudimentary state it can be translated as formal logic. However books on informal logic are better for preparing for the lsat because, much like the lsat, it has arguments and passages similar to that of the LSAT. Furthermore, all of the testprep companies and testprep booklets always give you an introduction to logic. So buy an informal logic book. it can seriously help.
The best-informal logic- book in the market right know is called:
Informal Logic: A handbook for Critical Argumentation by Douglas walton.
With powerscore there are clearly used techniques which are specific to each question type, you will only use formal logic diagramming on conditionals, parallels and, obviously, the odd formal logic question that is in the LSAT.
There are questions in the LR section that are pure formal logic and easily diagrammed. But there are many other question types, powerscore covers other techniques to attack these problems.
The PS LR techniques are involved and require a lot of time and practice, but they are flawless in the end. The record speaks for itself, hes an LSAT master.
A book on "informal logic" may help, but will be a waste of time, the PS author is well read on philosophy and logic and picks out the best bits and tailors it to the lsat.
Cut to the chase, reading philosophy may help but its not going to help as much as an LSAT expert focused program.
This Walton fellow seems somewhat credible, I'm sure he writes a half decent book here and there