Software Engineering
Best Kept Secrets of Peer Code Review by Jason Cohen, Steven Teleki and Eric Brown
Software Performance and Scalability by Henry H. Liu
Exploring Expect by Don Libes
Designing Data-Intensive Applications by Martin Kleppmann
Vagrant: Up and Running by Mitchell Hashimoto
Ansible: Up and Running by Lorin Hochstein
sed & awk by Dale Dougherty
Release It! by Michael T. Nygard
Mature Optimization Handbook by Carlos Bueno
Practical Monitoring: Effective Strategies for the Real World by Mike Julian
The Mythical Man-Month by Fred Brooks
Accelerate: The Science of Lean Software and DevOps: Building and Scaling High Performing Technology Organizations by Nicole Forsgren, Jez Humble, and Gene Kim
Erlang/Elixir
Linux/UNIX
How Linux Works by Brian Ward
The UNIX Programming Environment by Brian Kernighan and Rob Pike
The Design of the Unix Operating System by Maurice J. Bach
DNS and BIND by Paul Albitz and Cricket Liu
Javascript
Javascript: The Good Parts by Douglas Crockford
Interactive Data Visualization for the Web by Scott Murray
Bash
Advanced Bash Scripting Guide by Mendel Cooper
Ruby
Practical Object-Oriented Design in Ruby by Sandi Metz
Ruby Science by Joe Ferris and Harlow Ward
Multitenancy with Rails by Ryan Bigg
Testing with RSpec by Aaron Sumner
PHP
PHP and MySQL Web Development (4th Edition) by Luke Welling and Laura Thomson
Python
Dive Into Python by Mark Pilgrim
Foundations of Python Network Programming (2nd Edition) by Brandon Rhodes and John Goerzen
Practical Django Projects (2nd Edition) by James Bennet
Lua
Programming in Lua by Roberto Ierusalimschy
C/C++
Vim
The VimL Primer by Benjamin Klein
Modern Vim: Craft Your Development Environment with Vim 8 and Neovim by Drew Neil
Databases
Graph Databases by Ian Robinson, Jim Webber and Emil Eifrem
Learning Cypher by Onofrio Panzarino
Seven Databases in Seven Weeks by Eric Redmond and Jim R. Wilson
Data Science
Machine Learning
The Hundred-Page Machine Learning Book by Andriy Burkov
3D Graphics
Digital Lighting and Rendering (2nd Edition) by Jeremy Birn
Introducing Character Animation with Blender by Tony Mullen
Mastering Blender by Tony Mullen
Business
The Secret of Selling Anything by Harry Brown
The Lean Startup by Eric Ries
Innovation and Entrepreneurship by Peter Drucker
Getting to Yes by Roger Fisher, William L. Ury and Bruce Patton
Platform by Michael Hyatt
Linchpin: Are You Indispensable? by Seth Godin
Healthcare
Principles of Health Interoperability, HL7, and SNOMED by Tim Benson
Rockefeller Medicine Men: Medicine and Capitalism in America
Economics
The Use of Knowledge in Society by Friedrich Hayek
Ham Radio
The No-Nonsense Technician-Class License Study Guide by Dan Romanchik
Mathematics
Mathematics for the Nonmathematician by Morris Kline
Introductory Statistics by Barbara Illowsky and Susan Dean
Think Stats (2nd Edition) by Allen B. Downey