I've never heard of an eCookbook until now but the Stone Soup blog sells her books this way. Its funny some of these are the reasons I started this blog. It was mostly for me to be able to quickly find my own recipes no matter who's house I was at, and so that I could use the search function.  Anyway this is what she says:

Not Sure You’ll Use an eCookbook?
Here are 7 advantages of eCookbooks.
1. They’re portable and you can save them in multiple locations.
Work computer, home computer, other family members computers, iphone and/or ipad. You will always have these recipes at your fingertips. Perfect for last minute planning or for when you find yourself in the supermarket stuck for what to cook for dinner. Not to mention how much lighter they are when you’re travelling.
2. Find exactly what you want (and fast!) with the search function.Got mushrooms in the fridge? A quick search and you’ll have all the mushroom recipes ready to choose from.
3. Save time and jump straight to your chosen page with the hyperlinks.My favourite feature. Just click on the links and be taken instantly to your chosen page. The bookmarks help navigation as well.
4. Be inspired by browsing the interactive index(es).No longer are we confined to just organising a book by chapters. In my new book there are indexes to browse by the seasons, your mood, different cuisines, and recipe type.
5. All the benefits of Googling recipes without the risk or untrusted sources.Many people tell me they hardly cook from their cookbooks any more. They just use Google to find what they’re after. eCookbooks give all the benefits of an online search to access recipes from your favourite, trusted food writers rather than risking what Google throws your way from random strangers.
6. They can have more features than print books.Each recipe in my new book has at least 4 suggestions for alternatives to suit different dietary requirements AND just for fun. So even if you think a recipe might not be exactly right for you, make sure you check out the variation suggestions. But that’s not all the features. You can also buy a video version with video demonstrations for almost every recipe.
7. No need to wait or pay for shipping.
I don’t know about you, but I’m a fan of instant gratification. While a parcel in the post is lovely, not having to wait or pay for shipping your books is totally the way forward.