Chiming in with a: if you like books, maybe you can find some old O'Reilly books on ksh/Korn Shell that would be modestly helpful?

I guess O'Reilly doesn't publish physical books anymore, which is jaw dropping to me, but probably means you can find such things on the used market for not much money!

I realized, you asked about bash specifically, and ksh is not bash, but:

There are a plethora of UNIX shells and it's helpful to be versed in more than one!

I'm an outlier insomuch as I got habituated to tcsh long ago and still prefer it over most other choices (csh and tcsh users seem to be very fringe), even if I end up using zsh a lot these days.

CC: @stefano@bsd.cafe