Just to add to the comments- when you are studying the book/notes (I’d recommend studying lecture notes rather than the book), don’t just read through everything multiple times. You might already know this but I wanted to mention it just in case. It is a massive time waste and will do a very poor job of preparing you at all. A lot of research backs this up. The best thing to do is make flash cards or a quizlet for the information and then test yourself (usually using write mode so you really have to try and accurately recall the information). Recall practices are much much much better for studying and are very necessary! Practice problems also work as recall practices in this way which is why they’re also good.

I would: do homework problems, any sort of practice tests you can get, and then switch to making a quizlet based off of lecture slides/notes and practicing with that. Is it possible the professor was expecting you to be reading the book before classes/has he mentioned that things he doesn’t cover in lecture will be on exams? If so then it might be good to try and find chapter summaries in your textbook and add that information to the quizlet as well, but it’s definitely just not time efficient to read through 300 pages at this point!

Best of luck!!