Sam Munson’s 2010 novel “The November Criminals” was no great shakes—many readers noted that it seemed a debut written by someone who had read “The Catcher in the Rye” too many times—but the adaptation of it by writer-director Sacha Gervasi (who collaborated on the script with Steven Knight) so thoroughly defangs the book that the result is little more than a glorified afterschool special, and the fact that it’s strongly cast only adds to bewilderment about how it went so wrong.

The plot’s protagonist is Addison Schacht (Ansel Elgort), a senior at a Washington, D.C. high school who hides his grief over his mother’s sudden death with a show of manic energy. He’s smart and knows it, as the video diary he and his pal Phoebe (Chloë Grace Moretz) are filming shows: the entry with which the movie begins records him mailing his over-bulky application, complete with a twenty-two page essay instead of the requested three inches of typescript, to the University of Chicago’s Classics Department. In the book, he’s constantly spouting Latin and quoting Vergil; mercifully, that’s left out here, but also jettisoned is Munson’s portrayal of him as a small-time drug-dealer and a devotee of nasty Holocaust jokes. (In fact, the omission of those qualities makes nonsense of the title, which is never explained.) The movie’s Addison is a straight arrow, it seems.

After mailing his parcel Addison and Phoebe make a stop at a local coffee shop, where he banters in a show of literary sophistication with his friend and classmate Kevin (Jared Kemp), one of the baristas. Then they go off to Phoebe’s place, since she’s just requested that they have sex for the first time—she explains that she doesn’t want to leave for Yale in the fall as a virgin. In one of the movie’s few nice directorial touches, the camera remains focused on the coffee shop as the two drive away, their parking spot taken by a motorcyclist who, in a long shot, goes into the place and fires a gun. We later learn, as do Addison and Phoebe, that the man killed Kevin.

From this point the plot turns into a who-and-whydunnit. Since Kevin was black, the cops assume that the killing was gang-related, something Addison refuses to accept. He decides to investigate his friend’s death himself, despite the concern of his father Theo (David Strathairn), who’s still devastated by the loss of his wife, and the opposition of the school principal (Terry Kinney), who knows it will disrupt campus routine. Phoebe’s mother Fiona (Catherine Keener), a lobbyist, is also worried about her daughter being dragged into danger by helping Addison.

Yet Addison is undeterred. One might expect the movie to develop some excitement and suspense as he continues his inquiries, which eventually extend to meetings with several drug-dealers–menacing D Cash (Cory Hardrict), gonzo Noel (Danny Flaherty) and extra-twitchy Lorriner (Philip Ettinger). But it doesn’t, the scenes barely registering even as Addison’s drawn briefly into delivering drugs for information. Addison’s queries also take him to Kevin’s parents (Victor Williams and Opal Alladin), who tell him something unsettling that proves a key to solving the mystery—though, when it comes, the resolution is pretty flat and closure for Addison doesn’t really arrive until a sequence that accompanies the final credits, though whether you’ll want to stay around for that is doubtful.

Veterans Strathairn and Keener—especially the former—try to give some depth to the youngsters’ parents, but their efforts are largely unrewarded. The main burden falls on Elgort, who acts up a storm but can’t make either Addison’s cockiness or his fury especially convincing; there’s a pervasive superficiality to his performance that grows grating over the course of the picture’s eighty-five minutes, so that it’s difficult to muster much sympathy for the character when he’s put in jeopardy toward the close. Moretz has the more thankless role, which mostly consists of looking up adoringly at the taller Elgort as Addison fumbles his way through his search for answers. None of the supporting cast make much of a positive impression, with Hardrict, Flaherty and Ettinger veering toward unsavory stereotypes, as does Allie Marshall as a rich-bitch classmate. On the technical level the movie is mediocre, with washed-out cinematography by Mihai Malaimare, Jr. (though no one could have salvaged the video diary stuff). Editor Martin Pensa deserves credit for the brief running-time, though not much else; transitions are often muddled.

It’s doubtful that Munson’s book ever had the potential to become a consequential film, but it wasn’t inevitable that an adaptation should be as negligible as this.