or... don't try to read the books! your professors likely won't have read them (at least, not recently or thoroughly enough to test minutia from them).
and even if your professor wrote your book, his/her lecture will likely still only cover the material they deem to be important and the book will be redundant.
at my interviews, the med students i meet generally say that first years run out to buy the books for their courses, but in reality there is just not enough time to read them (and they have lecture notes/slides/syllabi to study to learn the material).