If you could read only one book on design, which would it be?

This one is priceless, can be applied to virtually anything:

Grid Systems Raster Systeme (Mueller-Brockmann Josef, 1957)

https://www.academia.edu/38930657/Mueller_Brockmann_Josef_Gr...

If I had to say, The Design of Everyday Things by Donald Norman: https://en.wikipedia.org/wiki/The_Design_of_Everyday_Things It is one of the only books I actually keep close to me and know where it is at all times.

Designing Data-Intensive Applications: The Big Ideas Behind Reliable, Scalable, and Maintainable Systems

Martin Kleppmann

It depends on the kind of design. For UI design, you can't go past: https://www.refactoringui.com/

Thanks for the replies, everyone!

Clean architecture