Pet peeve of the week: books with nonindicative titles. It comes to mind at the moment because I have the Mercy Thompson series on my e-book reader and I can never tell which book is which. I read the first four pretty much continuously but happened to take a break of a couple weeks before starting the fifth and last one, and I had to open every single book with that author's name to figure out what it was. Blood Bound? Silver Borne? Iron Kissed? Every book so far has included werewolves, vampires and faeries, so blood, silver and iron are mentioned at least briefly in every story. How in the world am I supposed to tell what order those books came in or what they were about?
Obviously, e-books are worse about this than paper books because there are no clues like cover art or descriptions on the back. But it can still happen with hard copies. I have every book in The Dresden Files series in paperback or hardcover, and I could describe from memory how vampires in that series work more easily than I could list the books in order by title. Let's see, Storm Front is easy, just because it's first book in the series; Fool Moon is the one about werewolves because they care about the moon, and the book about werewolves is the second book because Murphy doesn't trust Harry yet in it; Changes is the 12th and most recent book, because everything changes in it... and I could probably figure a few more out the same way... but overall, the names in the series are so vague that they could be any damn thing. Dead Beat? Almost every single book features ghosts, vampires and/or necromancy ("dead") and police work (that is, walking a "beat"). Turn Coat? Harry's coat is the most cool-looking thing about him (maybe the only cool-looking thing) and traitors of some kind have been big parts of half a dozen plots.
Way too vague. It can happen in any genre (Middlesex - the only clue to the story in the name is the pun), but it seems worst in urban fantasy series. Dead to the World, Dead as a Doornail, Definitely Dead - which came first? Which is about what?
My best guess is that these authors feel caught between serious fantasy and modern fantasy. Serious fantasy requires avoiding titles like "The Xs Sword" or "Curse of the X" or anything with the name of a monster directly in the title. Modern fantasy, meanwhile, can't mention feudal government or medieval architecture in the titles. If the author is lucky, something like that would merely sound too old-fashioned; more likely, it comes across as pulpish and unserious and/or a Lord of the Rings ripoff.
The problem is, exclude all of that and there's not much left that has anything to do with the story. Because come on here, we're still reading about wizards, werewolves and vampires. The writing may very well be very good and the product of great skill, but it's still a lowbrow genre. So what? Why not embrace it? Who's being fooled by vague titles? Would it have really hurt the authors all that much if they had used naming schemes such that, for the sake of argument, the fourth books in the series had been called Blood of a Faerie, Harry Dresden and the Table of Stone and The Amnesiac Vampire? Accurate, and descriptive unlike the actual titles, and kind of evocative.