I am currently using Storygraph, but I might switch to Hardcover. Their app is really good looking, if a bit slow, and it is very letterboxy, which I like. They too have lists feature which is a lot better than just tags, in my opinion.

I like storygraph a lot but… I have been using it for around 3 years and in that time nothing substantial changed on that website. They still don’t have normal author page.

Honestly, Valve should just ask for proof that you are 18+ if you want to sell items on Steam market or trade them.

Easiest solution IMO.