so you have CR, RC and SC books?
Powerscores Critical Reasoning Bible?
Manhattan Gmat Critical Reasoning?
Manhattan GMAT Reading Comprehension?
Manhattan Sentence Correction?
Kaplan verbal workbook?
you definately need more materials to study and practice with.
The guides are useless for an overview i think hence why something like Princeton Cracking the Gmat is good because its not a bad read and it gives a nice overall overview and introductions and explanations. Then you could try some of those guides and finally the last thing would be the OFFICIAL GUIDES.
looks like you not to improve 2.5 times more in verbal and about 1.5 times more in quantitative.