I finished the index yesterday and answered a few queries today. It is a compilation of names of modern and ancient authors, topics, and text references. I like indices myself. However, I am in a minority. At least we have an index. The publishers of my last book said that I could have either an index or the table I'd spent two and a half days creating!
To me, an index should be useful. It not only lists accessible topics and texts but also ideas discussed. That way, it is creative. For example, there might be a discussion of ideas about Jesus and the index will refer the reader to that page under "Christology." And I also like the feature referring to a related topic. So Lord's Prayer has its own entry while subtopics under "Jesus" include "prayer" with an entry, "see Lord's Prayer".
Does everyone know The Society of Indexers? There's also an American Society for Indexing. Between the two sites you can find everything you want to know about indexing.