I am a co-founder of an online Novel writing website, which is a Ruby on Rails website I wrote in 2012 and it’s been growing ever since. We have coaches, a community of writers, and are updating it using a studied process. We use A/B tests to continually verify the changes we are making so that our tweaks eventually get us more committed writers. Writers ready to finish their book.
Now Novel also has a Google Docs add-on that is currently under user testing and has some interesting updates in the pipeline. See it here: https://chrome.google.com/webstore/detail/now-novel/cbfimffhlobcbecokphhldpoehoejjpf