Doing revision of a book is OK. but the issue is, when we start writing a book, the version may be say 0.2, and when we release the book, the version may be 0.4. So the main thing is, the book got outdated in the release itself. So just think about our situation. Do we have motivation to write another book? I had this situation and I have changed the content of the book at the end of final edit. This is painful.
I have started writing in 2014 and done by 8th book in 2019 I guess. It was just a roller coaster ride. I really like the technology I am working on and very interested in writing tutorials. I think that was the main overriding factor of writing books even though it's having a lot of cons. Still planning to write a book, but this time I will go with self-publishing.
The issue is, if we are writting from 2020, we may publishing in 2021 or 2022. In the meantime, there may be lot changes in the technology that we are working on. So we may have to change lot of things in the book content even we finish all the chapters. This happened to me always. The version of software framework (ROS) is changing and to keep up the new version I will keep on changing all the chapters ( mainly commands and all).
I got an invite to write a book in 2014. Initially i thought it was very easy and can complete within 3 months. By this assumption, i agreed and start writting. When I start writting, i understood that, it is not easy at all. As a first time author, i was litterally struggling. The only factor that pushed me was, I already spent months for this, so If leave the project, I will lose that months. So I kept going.
After 1.5 years, my first book poped up and it was well recieved. Immediately after that, I got the next invitation to write second book. The thing is, the book subject was very good. So I agreed again by understanding all the cons of writting. I have spent 6 full months (full time for completing the next book. And I am keep on getting invitation and because of the experience of first book, I could easily draft the other books. It was a tough time for me too. Only less income, but only motivation was, I am doing something challenging and I am learning lot of stuff, also I am writting about the technology I like the most.
I'm an author of 8 books in Robotics. Here are some of the lessons I have learned from this.
Pros
1) Great visibility in the robotics community
2) Started getting good consulting projects
3) Started getting Royalties(Passive income)
4) People start identifying me in conferences
5) Got the invitation to do research in good universities
6) Got good patience which is very useful while working with the robots
7) Knowledge also doubled (I have to do a lot of homework in order to write things in the book).
8) Self-satisfaction to became an author
Cons
1) Time consuming
2) Need full-time dedication
3) Royalties are very low (only 17% of the book price)
4) Books will easily come online for free download. This will definitely demotivate us to write another book.
5) Books will outdate very easily (Technical books), so you may have to update it by writing a new edition.
6) Getting good income from books is like getting a lottery. It will only happen to a few people.