We have been watching monarchs this summer, so I read Anurag Agrawal's "Monarchs and Milkweed: a Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution" with a lot of thrill. Milkweed is trying to kill monarchs with latex and cardenolides, but monarchs sequester cardenolides for their own defence.
https://press.princeton.edu/titles/10944.html
The hardbound edition is excellently produced, well-written, and I want a copy for myself.
Agrawal's blog is great too: