Just ok
Most people take emergency medicine in their 4th year of medical school. This book is a good overview of the subject, but in reality you will have already heard all of this in your third year clerkships, what you need to focus on in this book is the emergent treatments for the conditions it lists. Since you only have one month of EM I'd recommend you either start reading this book ahead of time or just use this as a reference.
Blueprints Emergency Medicine
This book is great! Written by Harvard professors. About 2-4 pages per topic. Teaches the reader everything about each topic in a concise way. Very easy to read but covers a lot of information. Great to study for the boards. I wish I new about this book and the Blueprints series during second year of medical school!