I don't buy the Best American Mystery Stories every year (like I do for the Best American Short Stories, Essays, Science and Nature Writing, and now Nonrequired Reading). What I do is glance at the editor and at the authors included within. This year's edition is edited by James Ellroy (L.A. Confidential and the rest of his L.A. Quartet). And it has a story by Joe Lansdale, "The Mule Rustlers" --which is a great story, with a nice, humorous twist at the end-- (Lansdale is the greatest Texas writer whose name isn't McMurtry); and a story by Joyce Carol Oates, "The High School Sweetheart"--which is a story very much in her style, and somewhat 'experimental', but isn't as good as what she normally does. The best two stories in this year's volume is Brendan Dubois' "A Family Game" (great twist of an ending) and Daniel Waterman's "A Lepidopterist's Tale", which really only kicks in at the end, and reminds me of an Oates story. Stuart M. Kaminsky, Fred Melton, Annette Meyers, Michael Connelly, Thomas H. Cook, Sean Doolittle, and Joe Gores also have good stories within. What detracts from the collection: the fact that while these may be good stories, there isn't a whole lot of mystery to them; John Biguenet's dull story "It Is Raining in Bejucal"; David Edgerley Gates' mediocre "The Blue Mirror"; James Grady's unreadable "The Championship of Nowhere"; amd F.X. Toole's story "Midnight Emissions", which I was unable to finish. When reading the collection you'll notice an unusual amount of sports stories--mainly baseball and boxing stories (or maybe not surprising since Otto Penzler edited the two books those stories came from).
If you are looking for really good 'mystery' stories, you probably want to move along, but there are 11 really good stories (that's over half) to read. Some you would call mystery, some you wouldn't.