What is the best way to put a "how-to" book on the internet (downloadable?)?

Answer 1

Convert the book into a PDF file, and offer that book as a download. Using PDF, you can make the book so that it can not be altered, copied and pasted, etc by anyone downloading it. That helps you to control the content of the document.

It also has the advance that a PDF file is the same any any PC or printer, so you can format the document to look like a "real book", and it will print that way for anyone donwloading it.