I've been looking at books as well. The ones I used at my university were written by the professor. Her books are pretty good, but they are structured very different than books in Korea and all her pictures are from clipart. They are "You Speak Korean 한국말 하시네요" (by Haewon Cho, Soohee Kim, and Emily Curtis) And I like them. They are a little pricy at Kyobo, but they are better than most of the books there. They are actually college level and the authors do a good job explaining things, I thought.
I was considering buying the SNU books as they are the ONLY ones that look good. I tried the Yonsei books and they totally suck. For those books, you are paying for the pictures, not the education.
Are there any good books for the TOPIC test though?