I came across the Eat Your Books service this weekend. The problem they are trying to solve is that you don't have an easy way to search through dozens of (dead tree) cookbooks, whether it's to find a particular recipe you know you've made before, or to try something new with an ingredient in your fridge. What the site does is to index the ingredients of recipes from cookbooks, and make that available for you to search.
After reading a bit more about it on Chowhound, I found a 3-month trial membership code online and signed up. The first step is to tell the site which books you own, which magazines you subscribe to, etc. They support importing books by ISBN, but I wasn't about to manually type in all those numbers. Technology to the rescue! My plan was to scan all the barcodes of my cookbooks with my phone. I used the Barcode Scanner Android app because it supports a batch mode. After ten minutes of beeping, I had the ISBNs of all my cookbooks!
Excitedly, I cut-and-pasted them into the Eat Your Books import page. As I soon discovered, while the site pulled metadata and cover images for 95% of my books, it hadn't actually indexed them all. They rely on user votes to determine which books to index. So while award-winning books and titles by popular authors are on the site, some of my more obscure titles haven't been indexed (yet).
Besides books and magazines you own, you can also indicate that you have subscriptions to certain cooking magazines, e.g. Cook's Illustrated, and they will automatically add new issues to your bookshelf as they are published. Even popular blogs can be indexed and added.
I understand the value this site provides, but I'm uncertain whether I'll continue with a membership. For me, it's a good way to reacquaint myself with the cookbooks I bought long ago, but haven't even cracked open. But I haven't gotten used to the workflow of searching for recipes by ingredient using Eat Your Books, then finding the book on my shelf. I like to flip through hardcopy cookbooks, but I would also want a digital version as well, for searching.