The questions are of very high standard. They have been set with specific focus on to highlight very novel concepts. By doing the sums, if you follow all the solutions, you will learn a lot of theory. Surely, the questions themselves are not tough, but requires a lot of rational thinking and application of concept. Best test series you buy for your GMAT preparation. It is important to go through the solutions even if you have got the answers correct. The reason for this is that the questions themselves can be solved with a trick. You might have solved it the longer way so if there is indeed a short cut to solve the questions, you'll come to know about it if you see the solution.