Funny you should mention wikipedia. I started out by writing a heap of entries in wikipedia and ended up not being satisfied. Typically bots or random people coming in and messing up my researched and distilled summaries. Also wikipedia is a general audience, I wanted to target researches like me and programmers like the kid I used to be.
The book gave me a more controlled environment, and a permissive license feels like I'm still giving back in a useful way.