I have finished the content for my latest book, though it might be a couple more months before I hand it off to my distributors. There are several steps required to go from content to packaging.
Right now I am proofreading one topic at a time in Google Docs, while also checking once more to see if Google has found any additional grammar or spelling concerns. Then, one topic at a time, I am passing the content through Grammarly. Grammarly seems to do a little bit better than Google on grammar issues, though I think it has some false-positives. For example, Grammarly seems occasionally puzzled by jargon. Overall, however, I think it is about 95% accurate, and it is finding things that Google missed.
Next, I use Notepad to scrub all the formatting, hyperlinks, hidden text, etc. from the content. Then I paste the scrubbed content into Microsoft Word. While I would prefer to stay with Google Docs, one of my distributors insists upon MS Word. I could just convert straight from Google Docs into MS Word, but in the process of creating the drafts I sent to reviewers, I inserted hyperlinks, a table-of-contents, and other content that must be removed. By passing through Notepad to get to MS Word, I know that all I am copying is visible text.
Aside from MS Word being required by one distributor, MS Word also has a different grammar and spell check algorithm. Occasionally MS Word finds things Google Docs missed. Additionally, I find there are some things that MS Word catches that Grammarly misses, and vice versa. In a few instances, Google Docs suggested I remove a comma, Grammarly suggested I put it back in, and Microsoft suggested I remove it again. That is a rare combination.
Typically, Google, Grammarly, and Microsoft each find things the other does not highlight. I like this. I have been proofreading some of the topics in the book for nearly four years, and now Grammarly and Microsoft are catching subtle wording twists that had sounded just fine to me and to Google.
This sounds like a lot of extra work, but I think each step is necessary. I prefer Google and I modify the review copies in ways that my primary distributor will not accept. For example, a true ebook does not have page numbers, though reviewers find them invaluable. What I have found is that once I insert page numbers, page headers, or an automatically generated table-of-contents, both Google and Microsoft insert hidden text that is difficult to find and remove. I think the process I am using now works.