[Wiglaf]

The problem with glossaries is that I should be able to pick up most of what I need to know by simply reading the book. If I want to study something I own quite a collection of non-fiction. Authors do not know more than readers about what entertains the reader. While the content should reside with the author, the placement of additional information should be determined by the readers (as well as it can be determined).
Overly extensive glossaries are problematic as I should not require a great deal to read the story. Either the info needs to be made clear in the story or if it is clear, it does not need to be in a glossary.
*A glossary is definitions and pronouniations; additional non-required but cool background material at the back is different. I just do not want a dictionary of (insert conlang here), a biographical dictionary, and a geographical dictionary included. Besides, if your story is well written, you just might find that the majority of entries are unnecessary.