What are good books about MO theory that don't require a lot of math background?
I'd suggest the seminal Orbital Interactions in Chemistry by Albright, Burdett and Myung-Hwan Whangbo.

The second edition came out in 2013 and I'm sure there are many copies of the first edition around as well.

They focus a lot on pictoral MO theory - indicating how orbitals of different shapes and symmetry combine.

To truly understand MO theory at a fundamental level, it really helps to study some quantum mechanics (and thus mathematics) but you can grasp a lot from the approach used in this book.