I love it when I read a book and get transported to a different time and place. When the words on the page create a reality of their own that in the mind is virtually indistinguishable from memory. Even a memory that could in no way be mine. Such scenes if perfectly painted can feel like a vacation in my living room.
I've experienced that with several writers, but the one's that impress me the most are those who do it with historical fiction. For instance Bernard Cornwells "The Winter King" which told an Arthurian legend without any feeling of fantasy, it was incredibly realistic. I also recently finished Ken Follett's "World Without End" and found the setting to be incredibly detailed, even though it took place nearly 900 years ago. Whatever he did that managed to get so many details about the look and feel of Kingsbridge that long ago is what I want to do with my own work.
Therefore I am actively working on a time machine to transport me to the Mongolian Empire circa 1150's. I thought I had it the other day, but upon the first live test...well things didn't go as well as I hoped.