I read and studied this person's first book, his beginner guide to Korean, and I really enjoyed it. And with this, I've never found a more comprehensive and abbreviated text on Korean grammar. It is spectacular! The only reason why I can't give it five stars is because occasionally the book emphasizes more old-fashioned usages that some Korean students tell me are not as useable now--or the book will guide me to use some new grammar incorrectly, as in, for example, when the author of the book translates something in Korean as being equivalent to something in English when it isn't at all. Nevertheless, I've never come across such a wide variety of Korean grammar condensed in such a little book and with essential grammar exercises related to each unit. 한국어를 공부하기가 어려우지만 배우기가 재미있어요. (If I didn't type that correctly, blame me.)