Klear Textbooks in Korean Language: Integrated Korean
It is excellent. If you youtube people who are studying Korean, they talk about this series. It's very thorough. I have the beginning one book and workbook that I ordered from Amazon. The only bad thing is it doesn't have an answer key but if you have a Korean friend to check your work then you'll be okay. Also if you visit www.twochois.com you can find alot of good Korean books there. It is based here in Korea but they ship internationally.