>writing is the easy part and editing is the hard part, and I completely agree.
I don't necessarily disagree but a lot of writing (and often graphics/figures) is needed to fill a typical book. You're looking at say 60 to 70 thousand words for a 250 page book. I write a lot and people think of me as being pretty fast--though I certainly know journalists who are faster--but my typical daily output is about 1,000 words assuming I'm spending most of a day on it. Do the math (especially if it's a part-time thing).
I wrote a diary during the almost two years I spent writing and revising a book for Manning Publications. I muse about the trad pub process and my feelings on the great slog that is writing a technical book.
http://www.gitmol.com/blog/