I'm not saying that these are the best books of 2019, nor that they're my favorites published in 2019, but that they're my top five of books I've read this year. That's only about seventy books, so it's not a huge pool. Five is an arbitrary number - I read a lot of good stuff this year. This list is alphabetical. Four of these titles I first learned of the author through Twitter.
The Calculating Stars, Mary Robinette Kowal. This was on my list for about a year before I finally got around to it, and the only upside of waiting so long was I was able to read the second one shortly thereafter. I really appreciate how Kowal depicts anxiety/mental health issues, besides all the "breaking-into-a-man's-world" bits.
City of Brass, S.A. Chakraborty. I picked this one up kind of blindly based on a Twitter recommendation, was expecting a historical fiction book based on the first chapter, and then it spins full-on into historical fantasy, which is totally a good thing. This book made me rediscover my love of hibiscus tea. This was the second audiobook I listened to, and the narrator (Soneela Nankani) is wonderful - enough so that, despite the frustration of not being able to easily binge the end of the book and needing to Google the map to figure out some of the locations, I read the second one via audio as well. The third doesn't come out for another several months, and I have been super impatiently awaiting it. The first one stuck in my head for weeks.
Hidden Figures, Margot Lee Shetterly. This is the non-Twitter title; I (like many others, I'm sure) heard about this book because of the movie. I was curious about the book partly because I wondered which pieces were changed for the film, and the book was amazing. This book made me wonder where I'd be if I'd taken the math scholarship I was offered, and whether, if I'd been born a hundred years earlier, if I would have ended up doing math for astronomers. It also has led to me added a bunch of Black-history-related titles to my to-read list, since I (like many white people) am rather ignorant of large parts of what this country has done to its non-white residents and citizens.
Seven Blades in Black, Sam Sykes. This was the last book I read in 2019, despite it being the first book I've ever pre-ordered. And then Google emailed me when it was available, at midnight of its release day, and it was a work night, and I was good and didn't start it. This was probably a good move, since when I did sit down to finish it after our Christmas trip, I stayed up till 3 a.m. I will probably pre-order the sequel at some point. I really appreciated the way Sykes trickled out the pieces of backstory to build up the reason behind the revenge plot. Edit, 9/27/20: If you want a book in a similar vein whose author hasn't been accused of abuse, try Gideon the Ninth by Tamsyn Muir or any of the Murderbot books by Martha Wells.
The Tiger's Daughter, K. Arsenault Rivera. The narrative structure of this book switches back and forth between a first-person backstory narrative and a third-person present-time perspective, which I found effective similarly to how Sykes used the same kind of structure in Seven Blades in Black, but I'm now really curious how the next two books are structured, based on where the two main characters end up at the end of the first one. I also want to know so much more about the world Rivera is building in it.