I've always wanted an edible wild plant field guide. I found this one at the store I work at (Great Outdoor Provision Company) but they also have it on Amazon.
I bought it because the field guide is organized by season, so its pretty easy to figure out what you'll be able to locate and identify by staying in the section for the current season. It has good color photos, maps of growing region, and information about preparation. I am a little disappointed because its late fall and most of the plants that can be foraged this time of year (mostly roots) needed to be located while the plant was still above the ground during the spring and summer.
I am extremely excited by the prospect of making fruit leather out of wild strawberries in the spring.