The challenge is not writing a book, but letting it go.

I wrote Understanding SEO https://fullstackoptimizatio.gumroad.com/l/understanding-seo...

4 times. Each time it took me a year. The last time together with an editor. And I could have gone on, over every word, every sentence again. In the end my editor forces me. In the end you just have to publish it, otherwise it does not exist.

Still think I did good, even after more than 7 years I still sell a few paper and some more e copies per month just by WOM, so yeah, must be some value in there.