The shelves->books->pages metaphor sort of works for me. It lets me categorise my thoughts in a way that works for me. The lead dev is also really communicative, and it's been really easy to deploy and run. I've been meaning to try and find some time to contribute some hacks to it.

Ideally, I'd love a way to make Bookstack and Obsidian work together...

For me, it was a wiki/knowledge base - I've had dozens over the years as I've tried to find the 'right' one, but I'm currently a fan of @bookstack@fosstodon.org. My brain's not always the most reliable, and so my wiki becomes my 'external brain'. A lot of people are using things like Obsidian/Notion/etc in the same way.