What type of books to read to improve Academic English?
The best book is one you will actually read. Your English won't improve by looking guiltily at that tome gathering dust on your nightstand because it's a slog to get through. So yes, novels (in your favorite genre) are excellent for that purpose.

Academic English isn't that different from regular English. Once you have a firm command of English, picking up the academic style is just a matter of reading a few papers in your area.