Mark Twain has always seemed like a character to me, not as in an interesting guy, but as in a product of human embellishment. Just like Tom or Huck or Becky, he lived only in my imagination.

And yet there he is on the cover of the double summer issue of the Atlantic Monthly, on tour touting "A Murder, a Mystery, and a Marriage," his newly published story, featured inside.

For a critic, it's a development most daunting, if not downright disorienting: Just how does one comment on a legend?

Well, it's . . . good. Beyond that, who am I to say? He's freakin' Mark Twain!

And the task gets no easier. The Atlantic surrounds Twain's tale with commentary by Roy Blount Jr., himself not un-Twainlike in ability - although at least I know he's real; I've seen him on TV.

Blount seeks to place the novelette into context, not only of Twain - who wrote the piece in 1876, after "The Adventures of Tom Sawyer" and during a respite from "Huckleberry Finn" - but of his times: America's centennial, Sitting Bull's trouncing of Custer, the Tilden-Hayes presidential campaign that ended in a shambles similar to our most recent electoral travesty.

Twain's plan had been to provide the skeleton of a novel to his great literary booster, Atlantic editor William Dean Howells. The two would enlist other great writers of the day to simultaneously have a go at the same basic plot, and then the Atlantic could publish them all.

What was the author after? "If Twain had managed to get all these big and middling fish following `in procession behind me,' " Blount explains, "he would have set himself ahead of just about every considerable literary element in America at the time."

Though Blount at one point goes a little too deep for my taste - he notes the "macromechanics" of the work, "venerable comic-plot tradition," and "traditional three-part structure" - he is clever and artful, albeit perhaps too much so in his passage about Henry James, one of the writers Twain hoped to corral. It has a Jamesian cast that showcases Blount's pitch-perfect ear, even if it gives off the scent of showing off.

If you still have room for some writing about reading, you can check out Book magazine's roster of the "influential 10 people who decide what America reads." There's the obvious one (Oprah), and a well-known trio (authors J. K. Rowling and John Grisham, plus New Yorker editor David Remnick), but the other choices were more enlightening: Sessalee Hensley? Carl Lennertz? For all 10, Book's quartet of writers make their cases.

Worth a lot of words

If dissecting literature strikes you as too much work for summer reading, you can always just look at the pictures, an opportunity afforded by the subject matter of at least four magazines on the stands right now.

"How photography changed the world" is the cover subject of another summer double issue, this one by US News & World Report (July 9 and 16). It is full not only of famous photographs, but of the stories of the people who took them as well - from Cartier-Bresson to Edgerton, from Capa (Cornell) to Capa (Robert). There is plenty to the package that is illuminating, including a double-spread timeline that begins in the fifth century BC.

The August Jane shows she hasn't lost her attitude, beginning with the headline at the top of the cover: "Inside: more free stuff than Jenna Bush has booze busts (at press time)." You'll find a set of photos of celebs by celebs, which rises above a People-like premise with snatches of unpolished intimacy.

Photography is the foundation of DoubleTake, the quarterly published in Davis Square, and it remains solidly so in the summer issue, exemplified by the pairs of photographs presented by Mark Klett: He revisited the scenes of 90-plus-year-old pictures and reshot them to show the regrettable changes man hath wrought.

But the finer parts of this issue are the words that accompany Stanley Greenberg's photos of New York City's water system. Alec Wilkinson backs a passel of interesting anecdotes with a deft style: "The road passes at an angle, so the trailers have been indented to form a jagged line, like the third, fourth, and fifth fingers of a hand."

Vanity Fair offers up a scholarly back-pages trifle on Ansel Adams. In anticipation of the great Western photographer's 100th birthday next year, San Francisco's Museum of Modern Art has gathered 114 prints for a show that opens Aug. 4 and subsequently goes on a world tour (closest stop: New York City). Here's a sample from Vicki Goldberg's accompanying text: "The complex truth seems to be that Adams encoded a 19th-century idea about the land in a distinctly 20th- century idiom."

So much for avoiding literary dissection.