I highly recommend that you publish your book in both a paid electronic book version and ad-supported Web version. Those are two different mediums. Each of them has distinct advantages over the other.
It is fairly common for technical books to also be available in a Web version. I’m pretty sure that all of the last 10 technical books that I purchased were also on the Web in their entirety. For example:
Web Audio API by Boris Smus
I read portions of that book on the Web before paying for it, same as in the past I would read portions of a print book in the bookstore before paying for it and carrying it out of there. I paid to get these advantages:
quality — better user interface, no ads
convenience — offline access and lifetime access, because a website can go away at any time
honor the implicit contract between reader and author and publisher — the author and publisher basically said to me, “if this is the right book for you, if you find value in it, you are part of the book’s community, so please pay into the community’s shared production costs to support this book and also future books from this author and/or publisher.”
Because there was no metaphorical gun to my head, it wasn’t a grudging decision of “OK, OK, I’ll pay for the book,” it was a very positive decision of “you guys nailed it with this book, this book will really add value to my life, I want the convenient and high-quality version, and I am happy to put a little money in the book’s tip jar.”
The Internet is still young and electronic books are like tiny babies. The fact that a model of free sample chapter in your electronic book reader has been done a lot so far doesn’t mean that is the right way to do it for the benefit of either the reader or the author or publisher. The ad-supported Web version with a downloadable electronic book is actually much more like the print bookstore. In both cases you can browse the entire book before you buy, and in both cases, when you buy you get similar advantages of a higher-quality reading experience, more convenience, and honoring the implicit contract between reader, author, and publisher.
One problem today is so many authors — especially new authors — are doing all this writing, production, publishing, and promotion of their electronic book, and then they sell 3 copies because nobody loves that book yet. Nobody has really even seen it. If you have already written 5 best-sellers then maybe you can expect people to jump at buying your 6th book sight-unseen. But that is only a small minority of authors. For most authors, you are still trying to build that kind of relationship with your audience. One way to do that is a Web version of your book so that a broad range of people can read your book and get that relationship started.
An important thing to recognize is that your audience is divided into 3 significant parts:
enthusiastic readers who have enough money to pay for books, and generally like to pay for books
enthusiastic readers who do not have enough money to pay for books, but may one day have enough money to pay for books
people who won’t pay for a book under any circumstances, either because they don’t want to or because they can’t
I think the sample chapter method is focused on converting people from group 2 and 3 to group 1. The ad-supported Web method is focused on pleasing the enthusiastic readers in group 1 and 2, who are by far your best customers, and selling paid books to them. Group 1 will pay for your book now, group 2 may pay for your book later, and group 3 was never going to pay for your book anyway.
I did a lot of research on this, and the thing that really converted me to doing the ad-supported Web version plus paid downloadable version is the cost of advertising. It is really hard to reach people today because the market is so fragmented. I was looking at paying Google a lot of money to place ads for my paid version on other people’s websites in order to get readers to go and view a sample of the paid version and maybe buy it. But I realized that if I did an ad-supported Web version, that acts as an ad for the paid version, but Google pays me. Still have to promote the website, but that is easier because you can go to social media with a link and say here is a link to something you can enjoy right now, whether you go on to buy the paid version or not.
As for ISBN and book contract pricing issues, there are none. A website is not a book and does not have to have an ISBN, although you can apply one to the website version if you like. If you do, you use a different ISBN. A paperback book and hardcover book and electronic book (Amazon or iBooks) and interactive book (iBooks) of the same work have 4 different ISBN’s. So you may put your electronic book ISBN XXXXXXX123456 into Amazon at $5 and the contract prevents you from putting that same ISBN into Apple for $3. However, it has no affect on the website version which either doesn’t have an ISBN, or has a different ISBN XXXXXX654321.
Where to put your book on the Web is put it at your own dot-com that you create with something like Squarespace which gives you complete control over it without having to learn to be a Web designer. And you place ads on it through Google’s AdSense. Do a dot-com of your name (e.g. Ernest Hemingway) and put your book at a so-called “clean link” (no extraneous information or tech ephemera) like:
… and that gives you a very easy to remember, easy to promote, easy to type, easy to understand Web location that you can promote like crazy on social media and elsewhere. And of course you put a prominent link on there to the paid version(s). And then your next book would go at:
… and now your website is really becoming a destination for readers.