Except for a few warm and dry weeks in the summer; anybody outdoors is generally just a few hours from dying if they are wet. The remedy for this constant threat is: to stay dry, dress correctly and know how to instantly start and maintain a small fire. Fire means life in a survival situation.
This book presupposes that you know the basics of how to start a fire under normal conditions. If you haven't done this very often, I suggest that you research the topic and practice starting a fire in a fireplace without anything except: paper, matches, kindling and fire wood. Practice until you can do it instantly and reliably.
It is a lot harder than you think. Check out any Boy Scout manual if you need some tips or directions. Don't be embarrassed. Modern first world dwellers almost never have basic wilderness skills.