That is a good question, actually. In my personal experience, there will always be a few professors who "go by the book" and will test you only from the book and so on. And the people who "read from the book" will get better grades and such.

The idealistic suggestion would be that if you know the material well enough, you will be capable of solving these kinds of problems. In fact, the professor will teach from the book in his class right? At least take notes about the kind of stuff that he covers and study that. Yes, people with the books who have practice solving the same problem will find it easier, but you won't find it impossible either. And the test itself will be more honest, don't you think? :)

That's what I did in college, but I understand that not everyone will want to do the same.