- Design Systems by Alla Kholmatova - the canonical design systems book, in my opinion
- Expressive Design Systems by Yesenia Perez-Cruz - a great follow-up to Kholmatova's book
- Atomic Design by Brad Frost - written before we were using the term 'design system' for web interfaces, but many popular ideas extend from these ideas
- Thinking in Systems: A Primer by Donella H. Meadows - the canonical systems thinking book
- Systems Thinking for Social Change by David Peter Stroh - a good follow-up to Thinking in Systems with a bit of additional detail on system archetypes
- The Elements of Thinking in Systems by Albert Rutherford - focusing on system archetypes, this rounds out the other two resources nicely.
- The Design of Everyday Things by Don Norman - a pillar in design canon. Many of Norman's concepts and terms are a part of design vernacular
- Change by Design by Tim Brown - "Design Thinking" originated with IDEO, and there are some good lessons here. However, it is very anecdotal and can be a bit repetitive.
- Design Basics Index by Jim Krause - an introduction to basic design concepts
- Responsive Design: Patterns & Principles by Ethan Marcotte - one of the canonical responsive design resources
- The New CSS Layout by Rachel Andrew - the canonical CSS layout resource
- Thinking in Type by Ellen Lupton - a wonderful, in-depth discussion of typography – Elements of Typographic Style by Robert Bringhurst - the canonical typography resource – Interaction of Color by Josef Albers - one of the canonical color resources
- The User Experience Team of One by Leah Buley - This gets into the details of being a design researcher, but there's a lot to gain from having a high-level understanding
- Everyday Information Architecture by Lisa Maria Martin - a very helpful guide for understanding information architecture
- Accessiblity for Everyone by Laura Kalbag - a short, but comprehensive guide on building for accessiblity and inclusion
- Ruined by Design by Mike Monteiro - a good discussion of design ethics and technology
- Mismatch: How Inclusion Shapes Design by Kat Holmes and John Maeda - A good discussion on inclusive design
- Service Design by Andy Polaine, Lavrans Løvlie, and Ben Reason - a good overview of service design concepts
- Good Services by Louise Downe - another great resource on service design
- Nudge by Richard H Thaler - There's a lot of overlap in designing systems and behavioral economics
- Good Strategy Bad Strategy by Richard Rumelt - a systems thinking approach to strategy
- Designing for People by Henry Dreyfuss - much of how we think about design today goes back to the early days of industrial design, and Dreyfuss has a ton of great insights