HoTT is too big for my tiny brain, but Harper's book Practical Foundations of Programming Languages (PFPL) was hugely informative and is reasonably accessible t

HoTT is too big for my tiny brain, but Harper's book Practical Foundations of Programming Languages (PFPL) was hugely informative and is reasonably accessible to programmers who like some theory and consider themselves to be language geeks. The full text of the first edition was online. Now there's a second edition that is mostly online with a few parts missing, but that still looks good: https://www.cs.cmu.edu/~rwh/pfpl/ https://www.cs.cmu.edu/~rwh/pfpl/