I'd recommend the Nand Game[1], a schematic based version of Nand2Tetris[2].

[1] https://nandgame.com/

[2] https://www.nand2tetris.org/

One classic textbook is Patterson and Hennessy, Computer Organization & Design: The Hardware-Software Interface.

Learning how to program FPGAs (in verilog, etc.) is also a nice way for software people to start getting into hardware.