Does it mean that OG is sufficient for me to get a good GMAT score, I mean does the questions in this book have similar complexity as on the real GMAT exam?
Sufficient may mean something completely different to someone with the goal of a 600 vs. someone shooting for a 720. Will it prepare you? Absolutely, but I would review the Quant board because the experts here have some incredible threads and topics to guide you through any level of preparation you wish to achieve.
Similar complexity.. I can confidently say yes by the response from GC members that I would consider extremely informed. Similarly, the GMATPrep CAT's are also very similar.
Thanks, that is the answer I am looking for. I mean math is endless and it's having a huge complexity level, I just wanted to know the border line before which I guess I should stop myself so that I can prepare myself for other section too.
To answer you question about the target score, I dream of perfect 800 like everyone else but I see myself pretty good with 700, so can you recommend me other books too if required to achieve 700?