GitBook is nice and I would recommend that if you want something that works good for you out of the box. I personally write markdown files with typora and then publish that to my own notes setup, which is simply mkdocs and some tweaks.
I thought the fact that GitBooks has search is a nice and necessary touch. I'm going to have to revisit the static site / blog generators. It's prefer to publish to GL or GH, as well as (for that I have in mind) be able to accept PRs.