“Tell me,” Kurt Vonnegut asks Jane Marie Cox, his future wife, “would you enjoy living with me, sleeping with me, leading a carnival life?”

He writes from Camp Atterbury in 1944, where he is an enlisted 22-year-old intelligence trainee in the 106th infantry division. “My new job is to cover my face and hands with soot and crawl into enemy lines to see what in the hell they’ve got,” he explains.

It’s classic Vonnegut, one of many nuggets of dark humor in “Love, Kurt,” a collection of letters discovered by Edith, the couple’s oldest daughter, in the attic of the family’s home on Cape Cod. It’s a preview of the wild mind that will go on to produce 14 novels including the celebrated satire “Slaughterhouse-Five.” It also foreshadows the horrors that await young Kurt in Europe: He is captured during the Battle of the Bulge, listed as MIA for six months and sent to a Nazi prison camp in Dresden, where he survives the firebombing.

These letters are rich fodder, both as firsthand accounts of World War II, and a glimpse into the mind of a writer finding his voice. Above all, though, these are love letters, many of them so rapturous that were it possible to distill these pages into liquid form, it might be prescribed as an elixir for malaise.

They are also bittersweet: Kurt and Jane’s union lasted roughly 25 years, until somewhere in the wake of the breakout success of his sixth novel, Kurt left. “How could a love so dazzling and singular and determined fizzle?” Edith asks in the introduction. As we read these letters, which cover the couple’s early courtship, from 1941 to 1945, we can look for clues as to what went wrong — though the details are notably one-sided. Of the 226 letters collected here, there are just two from Jane: one a solicitation she sends to an agent on Kurt’s behalf and one lipstick-smacked letter to him praising his work.

Jane and Kurt had known each other for years before the correspondence began. They had gone to school together from kindergarten to third grade, in Indianapolis, and at age 19, reconnected at a country club social. Kurt began writing Jane while he was a (mediocre) student at Cornell and she was studying literature (more successfully) at Swarthmore. Some typed, some handwritten, these letters are adorned with whimsical sketches and amusing ephemera, such as the coupon entitling Jane to 1,728 “loving kisses to be bestowed, one each, on every square inch of her beautiful body.” He draws a floor plan for the bookshelf-lined one-bedroom “rabbit warren” they might occupy someday. Kurt woos a sometimes reluctant Jane, pleading with her to join him in the grand Vonnegutesque adventure he envisions: “Sideshow after sideshow — half truths, colorfully displayed, — the net effects of our rococo environments and educations; with intermittent Ferris Wheels and Lindy Loops.”

They will have seven children and a house full of dogs, he predicts. They might live in Mexico for a time, and both write for the New Yorker. Or live in Europe for a while and work as news correspondents.

It’s not all carnival: The letters involve plenty of number crunching as Kurt calculates living expenses. He jokes that he’s just opened a checking account at the Fletcher Trust Company, “with all the money I earned working for Adolph Hitler,” amounting to $458.98.

As with most stories of love and ambition, it’s complicated. There are references to misunderstandings, and there is something unsettling about the way Kurt tracks Jane’s menstrual cycles. Perhaps we ought not judge his tongue-in-cheek pledge to keep her “perpetually pregnant,” but it’s tempting. Weirdly, they do wind up with those seven children; they had three, and they take in their four nephews when Kurt’s sister and her husband die.

Amid all of this gushing from Kurt, one question looms large: Whither Jane? Jane graduated Phi Beta Kappa from Swarthmore and was fiercely literary. Kurt frequently speaks as if he and Jane are a team, referring to “our ambition to write great books.” He even suggests she is the more talented one: “I wish I could write as well as you.” But he is the one who begins to pound out words, while she acts as editor, secretary and cheerleader.

“It is GOOD!!!!!!!” she tells him of one story. “Darling, I am firmly convinced that you are the best writer on the face of the earth today.” He appears to need her support: “You scare me when you say that I would have been Shakespeare had I lived then. . . . Angel, will you stick by me if it goes backwards and downwards?”

Does Jane shape Kurt? A New Yorker article published five years ago, when the first small batch of these letters was made public, appeared beneath the headline, “How Jane Vonnegut Made Kurt Vonnegut a Writer.” Clearly Jane was influential. She gave Kurt encouragement and confidence at a tender age, and themes from these letters later find their way into his work. Presumably, Jane helped create conditions in a busy household that enabled him to write.

Would the manic creativity on display in these letters have thrummed its way into print had his love life taken a different turn? We are speculators here, peering into someone else’s marriage. Even as literary biography, voyeurism is voyeurism all the same.

“What I say in letters to you is particularly no one’s business,” Kurt writes from overseas. He is referring to the censors, and explains that he is withholding certain “poetic references” and “caustic comment.” It’s impossible to know the precise intention of these words, but it does raise the question of whether it is his desire that these letters remain private. But with the rich history they contain, having these letters made public is arguably part of the price of literary significance. In Kurt’s New York Times obituary in 2007, Jane’s name gets one mention, as the high school sweetheart he marries and divorces. These letters give Jane, who died in 1986, standing — even if indirectly.

“Love, Kurt” is story of two people deeply in love, living through what Kurt speculates are “the most horrible times in history.” It may be an exercise in delusion, but it’s still heartening to bask in these letters, to take this feral love for what it was at a freeze-frame moment in time.

Susan Keselenko Coll’s most recent novel is “The Stager.” She is the president of the PEN/Faulkner Foundation.

Love, Kurt: The Vonnegut Letters, 1941-1945

Edited by Edith Vonnegut

Random House, 249 pp. $35