So, by the inner bark, you mean all the stuff inside the outer layer?
Yes, the thin layer between the outer bark and the true wood body of the tree. An excellent write-up can be found
here .
As for a good books, the ones I mention
here are all good, though
the Peterson Guide to Edible Wild Plants should be everyone's first pick. For winter survival
this one is also very good for indentifying trees in the winter (though it doesn't say which ones are edible).
However to become an expert you need to build up a good library of plant books. Not just books specifically about edible plants but all sorts of plant ID books. Home Depot has a huge book on common yard weeds that I love. I've found cross-referencing many books to be the only way to identify every edible plant in an area.
As for pine nuts, while all pine seeds are edible only a few pine trees produce nuts/seeds worth the effort to harvest. Here in North America only pinyons, sugar pines and gray pines have big enough seeds inside the pine cones. All of these grow mainly in the southwest. I don't know of any which grow in places with true winter.
I probably should go outside and play with the cattails that grow everywhere around here.
I definitely recommend experimenting with cattails before you are stuck in an emergency situation. They are often hyped as a "supermarket in the woods" but in reality they are more of the "soup kitchen of the woods". You can get nutrition from them but it's not very pleasant. It takes a lot of effort and the results are usually bitter and nasty tasting.
-Blast