I haven't written a traditional book, but I'm currently working on writing Holloway's Guide to Technical Recruiting and Hiring (https://www.holloway.com/g/technical-recruiting-hiring/about). Writing is hard but my experience so far feels a lot more positive than the process described here. I had a ton of editorial support and we were able to get contribution (through interviews, reviews and edits, and even written contributions from a bunch of subject matter experts).

In any case, it's still not an easy feat and I have a ton of respect for anyone who embarks on (let alone finishes) the task of writing a book.