are there any helpful books that an entering M1 should get?

I have two suggestions that seem to be universal for med schools- first, you must get Netter or an equivalent with good anatomy illustrations- also I found the anatomy atlas from Rohen to be extremely helpful when the anatomy lab odors became overwhelming- it has dissected cadaver photos and is great for review outside of the lab.
Other texts seem to vary by school- I suggest asking 2nd years from your own school.

DO NOT buy any books until you talk to a upperclassman

Some good first yr books to use during your classes to prepare for the boards would be BRS Physiology, Lipincott biochemistry, High yield gross anatomy, high yield neuroanatomy, and I would recommend high yield cell and molecular bio only if you are weak in that area.