Backcountry First Aid is an excellent choice for a small manual or compendium about first aid treatments when you are in the outdoors. It is four inches by five and a half, and 120 pages long, so it will fit in a first aid kit or bag. The back cover has an "Action Index" that refers you to the pages for 47 different conditions or accidents. Topics like Bites and Stings, hypothermia, shock, water disinfection, etc, etc. The topics are covered very well - succinct and as comprehensive as you could hope for in a portable manual.
Of course it pays to read the manual before heading out, and in fact is valuable for anyone who wants to be ready for an accident or sudden sickness, whether in the wilderness, driving to work, or in your backyard.
Highly recommended.