This book covers a total of approximately 2,000 words according to the following criteria. Selected the vocabulary words appeared more than 3 textbooks from the language institutes of nine universities and two private institutes on the basic first and second level Korean.
When I first came to Korea and got serious about studying, I memorized all 2000 vocabulary words in this book. Every vocab word in here is a common everyday word. Each entry also contains a basic example sentence as well so you can see it in context. It was really helpful and gave me a sturdy foundation to work from. I highly recommend this book if you are just starting out in Korean.
There is also an intermediate version of this book, but I can't give an opinion on it. After completing my beginner textbooks, I learned vocabulary as I encountered it through context.