They found that elusive, perfect balance between familiarity and novelty. The sort of fantastic stories I already loved with the addition of refreshing, new authorial voices made them amazing books. They taught me to appreciate authors and creators outside of those I was already familiar with.
The most memorable volume was Bruce Coville's Book of Spine Tinglers. It had a story called "Past Sunset" that reached right in and pulled my heart out. Don't get me wrong; I'm not saying it was any better than the other stories in the series, but it was the one that stuck with me.