Hmmm, this is really hard because I read a lot of great books. I was going to say Enlightenment Now by Steven Pinker, which Bill Gates says is his favorite book of all time, but it came out in Feb 2018.
My choices are influenced by two things: I go for nonfiction and I'm interested most in the things that help us build Cake. One of the books that really got my attention was Twitter and Tear Gas, which looks at how protest is fueled and crushed by Twitter, and the Internet in general. Maybe it's on my mind because I just got back from March For Our Lives.