It can be anything STEM related, doesn't have to be directly software engineering. I'll start it off: Currently reading Serious Cryptography by Jean-Phillippe Aumasson
Architecting distributed systems is a "new" for me, which I want to get a good grasp on, sooner than later.
I'm currently reading Designing Data-Intensive Applications by Martin Kleppman. (dataintensive.net)
Planning to pick up Kafka: The Definitive Guide, soon after. (confluent.io/wp-content/uploads/confluent-kafka-d…)
Have a read of Alex Bellos’ ‘Alex’s Adventures in numberland’. Pretty good read if you are into your numbers.
I'm currently reading two books:

Clean Architecture: A Craftsman's Guide to Software Structure and Design
The book written by Robert C. Martin, also known as Uncle Bob, is a marvelous masterpiece. The author, best known for his other books Clean Code and The Clean Coder, shares his half-century experience and tells what choices to make and why they are critical to success.

Blood, Sweat and Pixels
The gaming industry is a fascinating place. It's a mix of creative and technological work and innovation. The results of technology's immersive evolution in the last 20 years can be best seen through the lenses of gaming. Nowadays, we take games for granted, but behind each game stays a team of creative directors, artists, developers, product designers, testers, which bleed and sweat just to please our own needs.
Blood, Sweat and Pixels tells the stories of some of the best known games like DOOM, The Witcher III, Uncharted 4, Diablo III and shares the difficulties the studios have faced. It's an inspiring book, full of lessons and stories about decisions and sacrifices.
I used to ..but the best book is industry of the future by Ross
Marco Alka
Software Engineer, Technical Consultant & Mentor
Currently reading WTF: What's The Future and why it's up to us by Tim O'Reilly. Very nice book!