This is a beautiful book and well worth your attention. I wrote a much more detailed review that got eaten by an HTML error (copy your writing before hitting the submit button people) so I'll just present the highlights.

1. Gorgeous prose and excellent pacing.
2. Garfield seems like a genuinely good guy, and might have made Reconstruction less nightmarish if he hadn't died.
3. His assassin, Charles J. Guiteau, doesn't seem insane to me. He seems like someone from a modern forum-driven hate group, like a white nationalist, gamer-gater, or an incel.
4. The American medical establishment also seemed crazy arrogant, ignoring Lister's antiseptic method despite clear life-saving evidence and a relatively low cost to institute.
5. And the doctor who took charge of Garfield also seemed damn arrogant. By Millard's account, it sounds like Garfield could have been shot in an alley and patched up by sawbones and probably would have stood a greater chance of living.
6. Poor Robert Todd Lincoln.

If you enjoyed this one, I might recommend Assassination Vacation, which covers this event but has a wider sweep. They have a surprising lack of overlap while still discussing similar topics.

I think I just became a Candice Millard fan. This book was engrossing.