smodak
I have read the Powerscore Verbal Book. I still cannot answer the assumption questions reliably. Are there any other good resource for the assumtption questions?
If you are looking for CR strategy:
Powerscore has a specialized book for answering Critical Reasoning questions Powerscore CR Bible - it is the best in the market.
If you are looking for practice questions:
OG-12
OG Verbal Supplement 2nd Edition
OG -11 (high overlap with 12th edition)
Once you have completely cracked each and every question in these books and are going strong - you can move on to some LSAT CR questions (much more difficult) and then GMATprep CR questions towards the end of your prep. That should suffice.
Hope this helps.