Norman Mailer’s new novel weighs in at just under four pounds and 1,300 pages, making it, if not him, a literary heavyweight champion. It’s about the CIA, and it suspiciously appears just when the fall of communism, which the CIA didn’t predict, much less engineer, leaves the agency looking a bit beside the point. Could it be a CIA plot? Here’s a fat novel by our most conspicuous novelist that turns the CIA into the stuff of epic, the key to all the secret chambers of the American soul, and, for all its pratfalls, still the most dashing thing going during the dim Cold War years.

No, the book is not a CIA plot and hardly even contains one. The CIA merely serves as a shelf on which Mailer can display his prize preoccupations. You can think of the novel as a prolonged meditation on how, during an American era devoted largely to conformity and consumption, one might have gone about measuring up to Nietzsche’s advice: Live dangerously. Mailer tells us that ”happiness is experienced most directly in the intervals between terror.” Much of the earlier and more imaginatively shaped part of the book is concerned with zeroing in on manhood by facing fear, a theme hammered home in bravura passages about rock climbing and other ordeals.

The transition from rock climbing to sex in Harlot’s Ghost is a smoooth one — both ventures invite confusion about which crevice to go for and both involve one beautiful conquest after another simply because they’re there. Still another theme — and a good one — is the inescapable duality in the nature of things, which obliges everybody alive to accommodate two skirmishing psyches and obliges God to accommodate the devil. But themes abound here, most of them sporadically compelling: power, lying, loyalty, fathers and sons and surrogate fathers, husbands and wives, ghosts.

The early part of the book — the part most resembling a novel — has Harry Hubbard, Mailer’s CIA alter ego (mostly blue-blood WASP, one-eighth Jewish, son of a Hemingwayesque CIA papa), guiltily returning, on a foggy Maine night, from his mistress to his adored wife, Kittredge (herself a part-time CIA agent). Kittredge, we learn, had carried on an affair with Harry while married to his urbane CIA mentor, Hugh Montague (Harlot). The dark night ends with a couple of mysterious deaths and a new betrayal.

As the narrative jumps back and then slogs forward through Harry’s coming of age and early CIA career in Berlin, Uruguay, and the Washington corridors where plots to invade Cuba and kill Castro are hatched, the book’s fictional characters are gradually elbowed aside by real ones — including John F. Kennedy, J. Edgar Hoover, Castro, Allen Dulles, and assorted spies and gangsters. Harry gets paler and paler, in spite — or perhaps because — of being taken to a sleazy Berlin S&M club by a warped CIA loose cannon, visiting all the best brothels in Montevideo, and sleeping with a stewardess who is the girlfriend of Sinatra, Mafia chieftain Sam Giancana, and JFK. Kittredge, kept at an epistolary distance during this part of the book, is the fount of Mailer’s dualistic psychology but lacks a convincing psychology of her own. Harlot, a mixture of suave cultivation and missionary zeal, fades in and out of the picture.

After the book’s fictional trajectory gets lost, it works, when it works, as back-alley and back-bedroom history. But there’s too much of it. The prose can be beautiful: ”Now, in March, the fields are dun, and the snow, half-gone, will be stained in the morning with the stirring of the mud.” It can also be taut, but it periodically sinks under the weight of Mailer’s accumulated research. Still, you can savor the tonic moments, skim through the rest, and go over the edge when you come across, on page 1,282, the vertigo-inducing words ”To Be Continued.” B+