37Signals co-founder and CEO Jason Fried:

You know, it’s really easy to publish short form content on a variety of social platforms. And individual blog posts on a number of other platforms. These are solved problems.

But it’s surprisingly challenging to publish books on the web in nice, cohesive, tight, easy-to-navigate HTML format. A collection of 20 essays can be a book. Or a company’s handbook can be a book. Or an actual book like Shape Up can be a book.

…

So we did something about it. 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. Each book gets its own URL, and navigating and keeping track of your progress is all built right in.