I have read a lot of books to learn what I know about Wild Edibles. One thing I will say is while the books are valuable and will teach you a lot there is nothing like being in the field. You will only really learn the plants and become comfortable with them when you get out in the field so do as much hiking and research as you can but finding a good book resource is also extremely helpful. This post is to give a little bit of insight on the books I have found most helpful.
Anything by Samuel Thayer is excellent. He has a site and a couple books. Sam goes into great detail about his experience which started in his childhood. His insights are extremely helpful because he lives it. He is not just regurgitating material he has read like so many authors. I try to emulate this in what I do. I want to experience it and then share the details with you. I really like his writing style as well.
I also have found John Kallas very insightful. I have his book on Kindle. Like Sam, he also gives great detail and he lives it. He is not just repeating things but is giving great insights from experience.I have many other books but nothing that is as complete or detailed like these guys.
I do have one of Petersons field guides for basic ID but it is only for basic beginning information. If you can find resources on wildflowers that is a good idea as many are edible or the roots are edible. If you get something that will ID the plants for you then you can research each you find to determine if they are edible or not.
I do have a page on my site for books but I have yet to do a complete review on each that I have used in my research. Perhaps one of these days there will be more about those I have found. One tip I would give is avoid any books that use the word complete in the title. There is no such thing.