TaskWarrior with a "book" or "read" tag and a note on where the title comes from.

For example, if I'm watching a conference talk and the speaker mentions a book, I'll quickly add it. I'll assign a higher rank to the recommendation depending on the talk.

I also do that for persons. If someone mentions an interesting person I don't know, I'll make an entry. This is also how I discover people.

My library has a pretty janky wishlist function (the software feels 30 years old) that I try and keep updated, also I use my Amazon wishlist.