I'm currently reading "Origin" by Stephen Baxter. I never bought it as a "survival read" but it does mention PSK's and the story revolves round a survival situation.
I was curious about a paragragh that mentioned making bread from pine trees. Here's the quote, has anybody heard of this or tried it?

"You could make rope for instance, from birch bark, pine roots or willow. Women baked pine bread made from phloem, the soft white flesh just inside the trees bark. You could drink the sap of birch if you had to."

EDIT
Heres the book and a few reviews:
http://tinyurl.com/2h9vo