I have become keenly interested in knowing all about James Garfield after watching Death by Lightning: please recommend some books to dig in deeper

We watched the Netflix series Death by Lighting and I had no idea Garfield was such a progressive thinker
If he had not been assassinated he could have been one of the most influential presidents in US history.  Garfield was by far the most intellectual and educated. Maybe he could have ended racism and sexism had he served a full term? not sure.
He also  was an accomplished mathematician, and wrote an original proof of the Pythagorean Theorem while he was a congressman from Ohio. He likely died of starvation and sepsis due to medical incompetence. The story is tragic beyond imagination. there is a NYT article that details how poor his medical care was, and this ultimately killed him, not the bullet