It is more of an introduction but I enjoyed 7 databases in 7 weeks from the pragmatic bookshelf (https://pragprog.com/book/rwdata/seven-databases-in-seven-we...).

I have also learned a lot from Aphyr's Jepsen posts about failure modes of mostly NoSQL databases: https://aphyr.com/tags/Jepsen

I enjoy following Daniel J Abadi (https://www.cs.umd.edu/~abadi/), for instance about distributed databases and transactions (https://dbmsmusings.blogspot.com/2015/10/why-mongodb-cassand...).

Thanks for asking the question, I hope more references show up as I would love to learn more as well.