After multitudes of trips around South Korea, my first copy of this book was so trashed from being packed and unpacked into my backpack that I had to order a new one. This book will get used, especially if you are spending a long period of time in-country for traveling or for work.
I've generally gotten to know my way around in my three years in Korea, but I still take my LP wherever I go-- it has provided some real gems from restaurants to tours to shopping.
My only pique with the book is that some of the maps are more general than useful for locating specific sites-- especially back-alley places in locations like Kyungju and Cheju-do. I usually make a point to get a local tourist map [these can usually be gotten cheaply--a few thousand won at most] for comparison.
This book is definitely worth the investment of a twenty-dollar bill or so.