There really is a market for this kind of book; and Kodan-sha have been at the vanguard of providing hands-on instruction for advanced students looking to take a serious plunge into the realms of 'real' Japanese writing.
The emphasis here is on 'real', in that these are fresh from the magazines with little editorial intervention. They are not 'watered' down nor stripped of their colloquialisms, erratic grammar, or other aspects that make them authentic examples of Japanese prose. Indeed, the selections here are all contemporary, mainstream (if also faddish) authors who enjoy a popular readership in today's Japan.
Michael Emmerich, an active translator, has culled an interesting selection of authors here. I must say that my tastes don't necessarily match his own: the authors here, to my mind, depict the kind of über-hipness that has defined the Akutagawa Prize over the last ten years. To my mind, you could find better examples of Japanese stylistics and the kinds of literary praxis that makes Japanese literature unique, but you can't fault Emmerich for going with the current herd of award winners. At the very least, you'll be reading the same laureates who fill the pages of GQ Japan and other trendy storytellers.
Emmerich's notations vary from the fascinating to the disposable. His command of Japanese syntax, undoubtedly, is superb -- but his annotations more often come across as 'close readings' in the mode of lit criticism than useful grammatical explanations. By and large, more grammatical explanations would have been useful. Often, we're given translations (which are always well done) but little in the way of analysis as to the particulars of the example. And, sometimes, when a grammatical explanation is offered, Emmerich slips into dense meditations on 'temporal flexibility' and other such discourses on time and space. They're interesting, to be sure, but I think they would have better suited an essay, as they can often digress too far from the task at hand: explaining the mechanics of grammar. One often things, 'Just the facts, sir', rather than the kind of metaphysical acrobatics that really would suit a book with a different agenda.
All and all, though, you can't go wrong with this book. For more 'classical' selections, I recommend Giles Murray's _Exploring Japanese Literature_ which surveys more canonical (and quite frankly more accomplished) authors such as Tanizaki and Mishima. I would love to see another book specifically address 'newspaper' Japanese.
Considering the demise of Nihongo journal, and the like, more books like Emmerich's would be appreciated. Indeed, for French or Italian you can subscribe to services that provide you with a book each month of an annotated novel from the bestseller's list. Something similar in Japanese would be wonderful indeed. Until then, books like this challenge and instruct, taking your Japanese to the next level.