Wednesday nights this summer the Somerville Theatre has been screening its Keep It Cool II series of double features. The last offering, “The Big Sleep’’ (1946) and “The Long Goodbye’’ (1973) is this Wednesday, Aug. 22.

In an age of binge-watching and all-access everything, “double feature’’ must sound as old-fashioned as “ice cream social’’ or “Victrola.’’ Ah, but for those with revival-house experience, few terms are as, well, revivifying. A great double feature is 1+1=3, taking the movies’ relationship to each other and creating something that much larger in the imagination.

The Somerville pairings this summer have ranged from the shrewd (“Gilda,’’ 1946, and “Robin and the Seven Hoods,’’ 1964) to the shrewder (“The Outsiders,’’ 1983, and “Foxes,’’ 1980) to the more or less demented (“Bullitt,’’ 1968, and “Beyond the Valley of the Dolls,’’ 1970).

As regards double features where the whole is greater than the sum of its parts, “The Big Sleep’’ and “The Long Goodbye’’ are hard to beat. What they have in common is Raymond Chandler and his detective hero, Philip Marlowe. “The Big Sleep,’’ with its tale of blackmail and multiple murders, was the first Marlowe novel, and “The Long Goodbye,’’ with its tale of murder and multiple betrayals, the last good one.

Each is idiosyncratic and slyly alluring, if just slightly off the canonical beaten path. A friend in her early 20s who’s TCM-savvy enough to have once had “Casablanca’’ as her favorite movie was unfamiliar with either. That relative unfamiliarity is part of the pleasure the pairing affords.

The second movie to star Humphrey Bogart and Lauren Bacall, “Sleep’’ has always been a little in the shadow of the first, “To Have and Have Not’’ (1944). Howard Hawks directed both. Chronologically, “Goodbye’’ came right between “M*A*S*H’’ (1970) and “Nashville’’ (1975), the twin peaks in Robert Altman’s reimagining of American film. It tends to get a bit lost in the Silver Age shuffle, though not as much as his “California Split’’ (1974). What a great double feature that would make with Paul Thomas Anderson’s “Hard Eight’’ (1996). Maybe next summer?

More than Sam Spade, more than Lew Archer, Marlowe is the Great American Detective. “Down these mean streets a man must go who is not himself mean,’’ Chandler wrote, “who is neither tarnished nor afraid.’’ That’s a bit much, of course, but that’s part of the appeal of the novels. A slightly rancid romanticism sits at their heart: a hard-boiled sentimentality. All the tough-guy patter and garish descriptions fail to conceal a wistfulness and moral nostalgia that make the books pretty much irresistible. It’s that Hollywood can’t-miss combination: raised eyebrows over glistening eyes.

How could the movies not go for this? Marlowe has been played by Robert Mitchum, James Caan, Robert Montgomery, George Montgomery, Dick Powell, James Garner, among others. In the niftiest bow to Marlowe’s ubiquity and stature, Dennis Potter used the name for the hero of “The Singing Detective.’’

Bogart, being Bogart, is the classic Marlowe, and “The Big Sleep’’ is the classic adaptation. Yet his presence works to subvert the movie. Marlowe remains subsidiary to Bogart rather than the other way around. That’s part of the fun of the movie. Already the Chandler/Marlowe legend was being erected, and “The Big Sleep’’ is something of an act of creative demolition.

One of the great Hollywood anecdotes concerns Hawks and William Faulkner (who did the adaptation, with Leigh Brackett and Jules Furthman) being unable to figure out who’d committed a particular murder. They called up Chandler, who confessed he was baffled, too. The story is emblematic of how confusion becomes a tone, even a velocity, that’s at once playful and glancing.

“The Big Sleep’’ is subversive in a way that few Studio Era features are, and not just Marlowe is getting subverted. The bookshop encounter between Bogart and a young Dorothy Malone is as sexy as anything in a Hollywood movie between the early ’30s, with the imposition of the Production Code, and well into the ’60s. Detective movies are supposed to be about finding out. “The Big Sleep’’ is all about knowingness.

Where Bogart transcends Marlowe, Elliott Gould turns him inside out. With his fuzzy-muzzy manner, Gould is more Beat poet than gumshoe. Don’t let the amiability of his performance fool you. This is genre insolence, and many reviewers hated, hated the movie when it came out. By then, Marlowe’s canonization had long since taken place. Where Hawks toyed with demolition, Altman goes for outright destruction.

Except that he doesn’t. The true glory of the novels is how they create a vision of Southern California — a place alluring and amoral, scented with orange and poisonous with pleasure — that endures. As a stylist, Chandler is showy and glumly self-aware. It doesn’t matter. He earned his place in American literature as many better writers have not, thanks to this vision of California as “the department-store state. The most of everything and the best of nothing.’’ As a moral geographer, only Faulkner (nice coincidence) exceeds him among American writers.

This is why “The Long Goodbye’’ may be the truest to Chandler of all the Marlowe films. Altman is superb at rendering a palpable vision of Southern California: from Malibu gated community to all-night supermarket to the valet-parking vacancy of downtown. The Marlowe novels are such LA books, and “The Long Goodbye’’ is such an LA movie.

The virtues of “The Long Goodbye’’ are not limited to LA evocation. There’s Sterling Hayden’s patriarchal magnificence as a Hemingway-like author or the uncredited appearance of a certain future governor of California. The latter is nicely bizarre, but no more so than John Williams’s brilliant theme-and-variations score. Even more than Gould’s spaced-out performance, Williams’s music may epitomize the movie’s pull-out-the-rug attitude.

The one bit of non-Williams music to appear in the movie is “Hooray for Hollywood.’’ Altman’s being ironic, but he’s not being ironic altogether. Having it both ways is central to why he’s such an important director, as well as a severe limitation.

Having it both ways is an aesthetic double feature? Something like that, yeah.

Hooray for Hollywood? Hooray for the Somerville.

Mark Feeney can be reached at mfeeney@globe.com.