Mayo clinic board review videos (search on youtube) and ACCSAP8 or 9 questions are good enough. Board vitals has 1400 questions if you have a VA that has a free subscription.
You can find pdfs of Braunwald review and assessment online which is good to learn concepts but not reflective of the exam.
Read through all 29 acc/aha guidelines found at acc.org/guidelines (knowing class 1 and class 3 indications are key for boards). I usually read the guideline that was pertinent to the rotation I was in.
EKG - for sure O'keefe is the only book I read. Unless you're going into EP, doing more is not needed
just reading through won't help as you'll gloss over a lot stuff and it won't stick. Making online flashcards via many free available websites would be quite helpful if that's how you retain info. Otherwise, having a list of specific questions/topics and trying to use active recall to see if you really know the stuff is key. Being familiar with info is quite different that actually knowing it. For example, I made a list of key questions/topics and ideas as I was reading thru (ex. what are class 1 indications for CRT-P) and would go back to see if I can actually list things out on a plain piece of paper w/o any help
