BookStack is described as 'Free and open source knowledge management platform built on PHP. The system has been built around simplicity to ensure that adding information to it is not a chore. The content structure is built on the metaphors of Books, Chapters & Pages' and is a very popular Wiki Engine in the development category. There are more than 100 alternatives to BookStack for a variety of platforms, including Web-based, Self-Hosted, Windows, Linux and Mac apps. The best BookStack alternative is Notesnook, which is both free and Open Source. Other great apps like BookStack are TiddlyWiki, Ibis Wiki, Docmost and Proton Docs.