The Gitbook layout seems a workable baseline --- the free level is moderately customizable --- I use it for: https://willadams.gitbook.io/design-into-3d https:

The Gitbook layout seems a workable baseline --- the free level is moderately customizable --- I use it for: https://willadams.gitbook.io/design-into-3d https://willadams.gitbook.io/design-into-3d The paid option includes an export to PDF which is okay for a quick print or free PDF to put on a tablet, but would need a lot of work to make a book.