Any tips on how to not forget books soon after reading?

I'd estimate that I read anywhere from 30 to 80 books a year, and looking back on all the ones I read even a few months ago, I feel I barely remember anything about them. Maybe some major plot elements, but often I can't remember any of the characters' names or more minor plot details. Going back a more than a year, I can't remember anything. All the books I had to read and analyze in high school (almost 10 years ago now) I don't remember anything even though I spent weeks dissecting those with classmates.

I hate to even bring up books I've read with friends because if they want to discuss them, it's like I haven't even read them and I feel like I come off as silly or a liar.

Is this common? Any tips for remembering books?