First off I apologize for rambling - I realized afterwards that I have created a lengthy commentary here - read it at your own leisure.
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As I've been reading this thread, I've seen more than one person supporting their arguments by calling into question the effort put forth by the author when they express a desire to include a glossary and/or map with their book. Though it may be unintentional, the main idea they bring up in their arguments seems to be an offensive ideal of "if you include a glossary or map, you are a lazy writer." There is truly no need to use this personal opinion as a basis of an argument spanning a collection of individuals. This does not, however, mean that you are barred from putting your two cents in and offering advice.
The question was that of "DO people read glossaries?" not "Am I lazy if I want to collect important snippets in the back/front of my book for readers to peruse at their own leisure?"
This subject matter is highly personal in each individual's opinion. You can quote statistics and sales trends all you want, but in the end, the result is going to come down to the individual reader, not any one person's outlook on what they think "should" be. We are not all as omniscient as we would like to believe.
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Divided from that side-commentary is my personal opinion on the matter. First off let me state that, to me, a glossary or map in a book does not make or break the deal for me. I'm not going to sit here thinking the author is a douchebag for cramming "unneeded information" into my neat and tidy little world.
I personally like the idea of glossaries and maps - maps in fantasy novels only by my view. BUT, they will only strike my fancy if they were done in a certain way.
A glossary (I prefer the term 'appendix' - it fits the idea of it not being needed but supplemental) in my ideal view will have expanded info on certain notes of interest that were introduced throughout the story. This may include but will not be limited to the "meat-and-potatoes" information which was disclosed during the narrative. They may also include characters, locations, items, factions, historical occurences and many other things which might allow me to glance into that imaginary world, if just a bit further. They will not, however, be neccessary to understand the main storyline in any way, shape or form. The purpose of the material will then be of an exlusively supplemental nature - it will be "neat" but not "neccessary".
As such, the appendix would not be something that is vital to understanding the story, and therefor I would never need to address it until AFTER I have read the narrative, thus eliminating the danger that the I would stumble upon a spoiler as they would have no business being near the back of the book, unless I decide to of my own volition. As a writer, I would feel that I have failed if the reader felt obligated (not inclined) to look to the appendix before they finished with my story.
Maps are just the same way to me. As I said before, I only expect maps in fantasy or semi-fantasy novels. For the most part, I don't have to absolutely know where things are in direct relation to eachother. It usually isn't vitally important to the narrative, unless there are military maneuvers taking place, in which case I would expect the author to be able to offer up such information concisely. Regardless of this fact, I enjoy seeing a well-drawn map at the front of a book, especially in a multi-book series. This presents me with several elements which may add to the overall experience.
The map might include only important features brought up in the story, but I find I enjoy it even more when locations and land features not mentioned in the story are also presented. This opens up the idea that, while the author did not utilize these locations within the present narrative, they may be used at some time in the future. It also lets my imagination fly - "What could this hamlet called 'Darian's Crossing' be like? What is its importance? Will the author bring us to it eventually?" Even if they're never used, I still find their presence comforting, after-all, I'll most likely never travel to "Normal Square, Pennsylvania", but it exists none-the-less, no?