Cardiac Surgery Essentials for Critical Care Nursing (search on Amazon
). It LITERALLY takes you step by step through the entire postoperative process for CV surgical patients, addresses multiple patient populations (CABG, OFCABG, Valve patients, Transplant, VAD etc.) and also has specific chapters on common problems in the CV population and interventions (postop bleeding, respiratory, neuro, rhythm, hemodynamics etc etc). I read this book in preparation for the CSC exam (passed first time no problem after reading the book), I had been a nurse for 2 years (started in CVICU as a new grad) at a high-risk heart center doing hearts all day every day and I learned a TON after reading this book (my only regret after reading it was that I didn't find it as a new grad). It's very readable (read it casually cover to cover in 3 weeks, although if you're new it may take you a little longer to get through the chapters) but the chapters aren't overly long, font size is reasonable, written very well, paperback. I'm sure all of the above books mentioned are great (I actually also had Manual of Perioperative Care in Adult Cardiac Surgery by Robert M. Bojar at the time which is like a bible for CV surgery) but this book is written specifically by nurses for bedside nurses in no-nonsense way.
Whatever book you decide on will be better than no book at all and I commend you for wanting to further your education being new to the ICU to take better care of your patients. Good luck in your new career, it's hard as a new grad but worth it 100%