Jason Fried introducing Writebook:

It’s a dead simple platform to publish web-based books. They have covers, they can have title pages, they can have picture pages, and they can have text pages. […] Writebook is our love letter to truly independent, zero-cost web publishing on the open web.

I’m playing around with this. I might’ve used it for my book if I hadn’t already adapted a Micro.blog theme for it.