This is just my suggestion. I've also bought Nova, but so far I've only went through their techniques and 1-2 questions that they have to illustrate the types of problems. I didn't do any of their exercises yet because I know those are real LSAT questions. I think the bad thing about that is you won't be able to get an accurate measure of how much time you actually need to finish an LSAT. Assuming you've mastered that question while studying the book, definitely you'll require less time doing it on the actual LSAT. Instead what I'm planning to do is do the actual LSAT first, and then go through the book to see if there are explanations for the ones that I've done incorrectly. Um..bad thing about this approach is it will require some extra time, but at least, you won't be frustrasted when you see the same questions again on the actual LSAT.
Hope this helps.