Though the Official Guides are a must for practicing the questions, you need to make sure that you supplement them with books which make you conceptually strong.
If you go through my post, you'll see that I had almost the same scores as you do on my first attempt and I was able to manage a 740 eventually. If I can do it , you should be able to achieve a 700+ . Generally, each test prep company has a couple of books which are really good. For example, I found MGMAT Math Guides and MGMAT SC Guides to be really helpful. s However, their CR and RC books weren't very useful. If you're looking at catching hold of the rules and the grammatical concepts essential for tackling difficult questions on the GMAT confidently, you'll find Aristotle SC Grail to be pretty helpful. I think that after doing MGMAT SC Guide and Aristotle SC Grail properly, you should be able to tackle SC more confidently as you'll not be relying much on what sounds correct. For CR, I found PowerScore CR Bible better than MGMAT CR book. I think RC is more a function of practice and how much well read you're . Go through strategies on RC and keep yourself a daily dose of 3-4 passages.I think if you keep doing it for 2-3 months, you should see a good improvement in your RC accuracy.

Thank you very much. I was feelling quite depressed after my score on the gmat! your story is really motivating, i think that i'm going to follow your suggestions and some other on this good website! Thank you again!