We Contain Multitudes by Ed Yong is about microbes inside us and animals and I have no idea why I read it, but it was difficult to read because I'm terrible at biology. Still cool though
Edit: Oh, I didn't realise this is the fiction comm. Oops. I guess I don't read any challenging fiction books. Maybe I should rectify that
I don't usually buy physical books anymore, since I realised that I'd get better value for my money if I only get books that don't really work on a Kindle, like illustrated books. So recently, I bought The Middle Ages: A Graphic History by Dr. Eleanor Janega and it's pretty good! It's basically an introduction to the Middle Ages and it does a pretty good job at providing a overview of about 1000 years of history. This book got me interested in the Middle Ages enough that I feel like reading all of the Dan Jones books I've had in my TBR for ages now.