Jeongdok Public Library
At the Jeongdok Public Library there are a little more than 4,500 books in foreign languages, nearly 3,800 of which are non-fiction, and all of which may be taken out of the library's facilities.
The library has 25 different magazine titles available for foreign visitors, including Time, Newsweek, Reader's Digest and National Geographic.
Namsan Library of Korea
The Namsan Library has a little more than 12,000 books in English, and more than 1,300 of among them have been purchased since 2007.
All registered members of the library can borrow books here. To register, an alien registration card is required for expats.
National Assembly Library
The official library of Korea's National Assembly offers about 263,680 non-fiction selections, plus about 2,000 fiction publications in English....To get there, take subway Line 5 to Yeouido Station, leaving through Exit No. 2.
Visit www.nanet.go.kr/english for more information.
There were one or two other libraries listed as well. I know a continuing education library in Sokcho has children's books in English. I wonder about other libraries locally. Kwandong University's library has a (relatively) large, and varied, selection of English books, all thirty years old and older. I'll try to update this as I find out more.