I went through this book in a couple of weeks. Limited myself to no more than 2 minutes per problem (but often averaged 1 to 1.5 minutes per problem).
Ended up with 90 percent of the problems right (However, only 38 out of the 50 data sufficiency problems which always seem more difficult to me).
Can anyone comment on the difficulty of this book vs. that of the actual test (or OG for that matter).
I have not limited myself in time when doing the problems; just did them as good as I could - as a rule, they are fairly standard. The Difficult section is definitely harder than OG, however, as to the GMAT, the difficulty there will be that you will face some un-familiar problems. What I mean is some weird stuff you never saw and will have to come up with a solution method from a scratch vs. some hard work problems or probability. Also Kaplan
has no probability or combinations. I would say you are doing very good