Welcome to Catholicism and CAF, @baileym!
I am fairly new to Catholicism as well - 4 years only. I wish I could assist you with good introduction books, but I cannot. There is so much out there! Currently, I am reading Aquinas’s Shorter Summa. It’s by no means an introductory text. It’s also pretty dense. It is not unreadable, though. It’s just dense.
I’d stick with the readings they are giving you in RCIA for the moment and, if you’ve not obtained a copy of the Catechism of the Catholic Church, as @Francis recommends, I’d get one. It has the foundations of Catholicism nicely articulated. It’s not the most entertaining read, but it is quite informative.
If you’re in the U.S., you’ve probably received a copy of the CCA, Catholic Catechism for Adults. That’s a great introductory text. If not, it’s a great starting point.
Good luck with your faith journey!