Students in the past have found this online book quite useful
If you are taking this class and thinking about taking ML later, I recommend reading chapters 2 and 3 of this book (free).
(It's a great book but please be patient with it, it's not the easiest book to read in particular if this material or math notation is new to you)
If you are leaning toward data science, this book is a good resource (free, part of Free ECE Textbook Initiative)
If you are taking this class as preparation for information theory/communication/signal processing/control, I recommend this book
If you are unsure what you want to take next or looking for a generic treatment of probability, I recommend this book, written by a mathematician for engineers