Notion is a commercial product and I'm just guessing but probably vendor lock-in in the long run.
Also it seems to be focused on team work and not managing papers/books. So as good as using this you could also use any other wiki software or database to do this.
# Calibre - Has server solutions to host your library easily - Is made for managing books etc. - It's open source and has a big community as well as plugins (https://github.com/kovidgoyal/calibre)
Don't get me wrong here, Notion looks like a great product and in my opinion it could be the next big thing in project management if marketing keeps up and they can convince the right people.
Only thing I really dislike about Notion so far: - It's not Open Source :-p (I'd love that)
For other things I'm sure it's awesome.