Link and Gaiman
Although I struggled through Magic for Beginners and only felt slightly more competent while reading Stranger Things Happen, I must say that Link prepared me for reading American Gods. That Laura is dead/not dead and follows Shadow around didn't even cause me to bat an eyelid. I am much more comfortable with the worlds of zombies, the absurd, and the paranormal because of Link. Even though I did not like it at the time, I appreciate it now immensely (kind of like Wuthering Heights) because I was able to delve more easily into the world Gaiman created.