Series: Hankuk Kiwon Mastery Series (10 volumes)
한국기원마스터시리즈 1-10
ISBN: 89-7990-126-7 (series)
Author/Editor: Hankuk Kiwon 한국기원
Publisher: Hankuk Kiwon 한국기원
Published: 2001
Publisher Recommended Price: KRW6000 each
Title: Vol 1 – Invasion and Reduction Mastery
침투와 삭감 마스터
ISBN 89-7990-129-1
Title: Vol 2 – After Joseki Mastery
정석이후 마스터
ISBN 89-7990-128-3
Title: Vol 3 – Attacking and Splitting Mastery
공격과 타개 마스터
ISBN 89-7990-127-5
Title: Vol 4 – Ladders and Nets Mastery
축과 장문 마스터
ISBN 89-7990-130-5
Title: Vol 5 – Capture Race Mastery
수상전 마스터
ISBN 89-7990-132-1
Title: Vol 6 – Life and Death Mastery
사활 마스터
ISBN 89-7990-133-X
Title: Vol 7 – Ko Mastery
패 마스터
ISBN 89-7990-134-8
Title: Vol 8 – Tesuji in Joseki Mastery
정석의 맥 마스터
ISBN 89-7990-135-6
Title: Vol 9 – Probing Mastery
응수타진 마스터
ISBN 89-7990-136-4
Title: Vol 10 – Direction of Play Mastery
방향감각 마스터
ISBN 89-7990-137-2
This is supposedly the current best selling technical reference series from the Korean Baduk Association (Hankuk Kiwon).
Tchan001's Blog 
I have a quick question about the format of these books and the Discovery of Method series, too.
Are they in problem format? Or would one need to be able to read Korean to understand them?
The Hankuk Kiwon Mastery Series are in problem format so it is possible to get some ideas from them. But the explanations look to be quite involving at times.
For the Discovery of Methods series, I think you’d really need to know Korean to understand them. These books seem to talk about very high level concepts.
Unfortunately I don’t know Korean at all so I can’t really tell you more than from just a cursory look.