Thanks for all your replies. HDSTEELE, you mentioned you've bought the book already..I also bought Master the LSAT...can you see if their approach to LR is similar? I'm having most trouble on LR so I'm trying to explore different techniques for that section. Do you think Prof Dave is doing a good job on that or is his approach just the same as the other prep books? I'm not actually doing any questions from the prep books (eg Kaplan/Princeton) because I know those aren't real LSAT questions. So I borrowed those books and tried to just learn their techniques, which seems pretty much the same. So if the book's technique only gives the basic idea of what to look for...ie logical fallacy, assumptions, strengthening/weaking evidence, inference, then I probably won't buy the book because I'm pretty aware of the different types. I actually found the 'Official LSAT with explanations' very useful. It explains why the other 4 answers aren't right, let you know the difficulty of the question, and suggest an approach for that type of problem.
Thanks again for all your feedbacks