yes, acorns are edible, but you have to do a lot of work to make them so. Too much tannic acid (a powerfull laxitive). Soaking them in water, with several changes for several days or until the water no longer darkens (tannic acid is what makes the water black and stains things black under the oak trees). The indians would just put all the gathered acorns in baskets and sink them in a stream for a few days or so. Once they are clean, they are easy to prepare and last a long time when ground and stored dry. Since they are usually used ground up, and they are a nut, flour made with them does not rise, but has more of a tortilla like consistence, or cornbread. Good for adding to stews, soups, and other dishes. Usually used a base for a dish and not the whole dish.
Classic indian recipe was acorn poridge with venison (or other meat), add what ever flavoring to the mix you like. Pretty tasty with wild onions.
add berries and maple syrup etc.
