Room acoustics basics

After I purchased speaker cables from Morrow Audio I received an offer to sign up for their Tweaks Newsletter. I received the first one and it was pretty basic ( what the OP wanted ) yet informative. It quickly and informatively described treating the wall behind the speakers and the wall behind the listener with easy to obtain and affordable materials. You don't have to make a purchase from them to subscribe to the newsletter. Just go to:

I used the book Master Handbook of Acoustics. Loads of great information.

agree with @willy-t  on Jim Smith's "Get Better Sound".  Much of his very understandable non-STEMmy book focuses on room acoustics and how the room is the #1 component in your system.  Worth the purchase--helped me a great deal.

Check out some Ethan Winer YouTube videos.