If you are interested in trauma care under fire, then 68W Advanced Field Craft: Combat Medic Skills is an absolute must in your reference library. This book lays out the essential information on Tactical Combat Casualty Care (TCCC) in an easy-to-understand format.
Written for military combat medics, this book does a very good job of explaining how to recognize and treat the common injuries that soldiers encounter in the modern battlefield. Many of the injuries are the same or very similar to what police officers encounter. A cop should not consider himself a paramedic after reading this book. However, if he or she understands and practices some of the procedures, he or she might be able to apply a life saving tourniquet or recognize the symptoms of tension pneumothorax in a fellow officer who has been injured.
By necessity, the book does use medical terminology. However, it is still very readable and useable by the non-medical person. The illustrations are clear and really help to make the text more understandable. Photos of actual wounds are included in the book (if you are squeamish about those, consider it stress inoculation.)
If you have an interest in self-care, this is a good book. If you are an instructor who is planning on introducing some form of realistic care under fire training in your department, this book is a must buy. Even if you have to come out of pocket, this book is worth every penny.
I paid more than $100 a few months back for this book. However if you click here to get your copy, Amazon is selling the book for about $85. Feel free to post in the comments if you find it cheaper anywhere else.