Noticed nobody responded to you yet and the post is just about a month old aka you still might be looking. :)
The concrete Corpsman side, local Sailors, SAR or Marines will probably help you with in a more erudited way.
If this is 'just' solid for combat medicines resources -
If you are beginning, A&P coloring books are invaluable.
Getting anatomical & physio terminology down solid, or half of the stuff you learn won't make sense.
If you can get a good anatomical atlas or a 3D model for whichever system you are studying, also helpful. Almost a necessity when you get to the skull to learn it right.
Coursera has a few low cost medical courses, by John Hopkins uni. Good for spatial orientation and a sense of how bodies look from the inside; becomes invaluable when one's learning things as how to intubate.
Super useful book, Emergency War Surgery, 5th Ed (recommend current ed, prior versions needed relevant corrections.)
Definitely have THAT one as a reference guide with you, at least one per company. Well organized, no nonsense, hands down, easy to study.
I'll look more at exact titles of others, since say radiology textbook don't remember even the author, but yeah.
Might help what level you are at / theoretically and things you already performed in field, eventually how you learn best, as not all resources fit the different learning styles.
The HM-ATF program is very cool, and something some of us have LONG requested.
Corps school (and FMF, if you go the Recon IDC route) are not rocket science. I would read some entry-level A&P, environmental medicine/hypo/hyperbarics medicine stuff, and maybe some basic first aid/trauma, because you are at 'A' and have a long way to go to A-school. Anything you read now is going to be foggy when you try to recall it in how many months.
If I were you, I would be a PT stud, read the bluejacket manual, make boot as easy as possible. Knowing what a tracheal hook is now isn't going to keep you out of trouble, but not knowing your general orders will, and a lot sooner.
Edited to add, read books about corpsman, learn our history, read that kind of thing.