I think technical subjects are great for e-books and to market over the Internet. The question is, which format are you considering: pdf, exe, or another format? You'll really want to tailor the format to your users - which format will most benefit them and the way they use your book.
I know it may seem strange to think of that now, but I always recommend people consider that before they get to involved in writing their book - the way you format and set up your pages depends on the e-book format you use. You don't want to go to a lot of work formatting the pages to look and act exactly how you want and then have to redo it becuase of the file type of your e-book.
If I can be of any more assistance to you, please don't hesitate to ask.