Official GRE Quantitative Reasoning Practice Questions: 1 Paperback – 16 Aug. 2014

Extra practice questions not in the general guide, and - more importantly - explanations for each question.

I would say that they could expand its question range; the initial preparation is the same as the main Official GRE textbook. However, all the questions have thorough explanations

Some of the questions were answered. In ink. Not a lot, but still an issue, because it's a practice book.