On the IndieWeb front there are some interesting evolving examples and state of the art documented at:

https://indieweb.org/personal_library
https://indieweb.org/read

In particular, I quite enjoy the micropub client IndieBookClub for posting reading updates to my WordPress site (it supports other platforms with Micropub support too.) More details: https://indieweb.org/indiebookclub. Here’s an example of how I’m tracking what I read on my own site: https://boffosocko.com/kind/read/ or if you want just the books.
If you’d like a non-WordPress hosted solution, you might take a look at Manton Reece’s excellent Micro.blog platform which has a nice book/reading UI: https://micro.blog/discover/books or https://micro.blog/discover/books/grid. (It uses IndieWeb technologies including micropub, so you can use IndieBookClub with it. You can also syndicate to it from your WordPress site if you prefer to have your own infrastructure and just join the community there for the conversation.)
I’m happy to help if you’d like further tips/pointers for any of the above.
On the Mastodon front, you might take a look at Mouse Reeve‘s Bookwyrm (GitHub) which is one of the best custom set ups in the ActivityPub space.