I’m in a similar boat and have been using the quarantine to study. I checked out a book at the base library and it was ok but my Lt. Recommended “Officer Candidate Tests for Dummies” and I enjoy this book way more.
It has clear break downs for getting the answers to questions and has a lot of tips and strategies for preparing for the exam. I got mine from barns and noble before everything shut down but it’s pretty cheap on amazon. Good luck!