I used GitBook to collaborate with other authors on my book quite related to the subject, Docs Like Code (https://docslikecode.com). I loved the ebook output but for print I had to use additional tools.
Pros:Lets authors use a development-like workflow
Cons:Some of the plugins were outdated or unmaintained; PDF was not print-ready to my specifications.
Totally love the new version of GitBook. It makes writing my first book so easy and fun. I wish more people will adopt GitBook.
Pros:Great user experience (fast and responsive), feature-full (code snippets, search bar)
Cons:The concept of "spaces" is somewhat confusing.
If you have a project that entails many chapters or is organized in an outline format, this is super-helpful. I love Git Book. Totally underrated software.
Pros:Open Source, easy to use, minimal UI, perfect tool for what it's meant to be used for. Lightweight.
Cons:Hard to think of any. It's under-rated.