"Shigley's Mechanical Engineering Design" is a great textbook if you want to learn the most you can with the fewest books about designing mechanical structures

"Shigley's Mechanical Engineering Design" is a great textbook if you want to learn the most you can with the fewest books about designing mechanical structures and moving parts from a strength perspective. Fluid flow/ thermo would be the other main academic area that this book wouldn't cover. There's a bunch more topics though that you build over years of intuition- manufacturability, design tradeoffs, etc.