What about some different models? While the internet/google presents everything, a well organized and to-the-point book still saves time and time is everything.
1. have your own website, and write online book only, ask people to pay for read?(free samples at the frontpage). 2. whoever paid can get automatic reminders on new releases, book updates 3. create a small forum on that site for questions and erratas. 4. give a link for whoever read your book somehow without pay, tell them if the book helped them to profit somehow, please press the donate button to show a little appreciation.
As there is no other costs involved(other than hosting fee), your book can be cheaper, to the point people might want to pay even though they can get a free version somewhere.