Happy to answer any questions about the process of writing a book! It's been a surprisingly fun side-project that brings in some money too.
A couple of questions, if you don't mind.
How did you support yourself while writing the book? And if you were working another job, how did you find time?
Did you try any other marketing like giving away the first chapter or blogging/newsletters?
I've been toying with the idea of writing a book on programming AVR microcontrollers for a while, since most of the information online is horrifically fragmented. I'm tempted to go down the website route and then publish it separately as a cohesive ebook, but it looks like leanpub may be a good option if you can publish individual chapters as you write them.