Food For Free
First published in 1972, it has been a regular bestseller in the countryside/gardening categories ever since. A colour edition was published in 1989. It's a Collins Gem book, which are pocket sized, ideal for keeping in your backpack or coat pocket, and features all types of plants and fungi that can be found in the British countryside and are edible. But even if you are miles from the nearest hedgerow it is still a fascinating read, with loads of interesting facts. It is available on Kindle as well, although this sort of book is probably better as a printed book, where you can quickly skim through the pages, when you are standing in a drizzle.