“I give them five years,” announced a bridesmaid. Ada Calhoun agreed with this cruel prophesy about the couple whose wedding they were about to celebrate, but she was not going to share her gloomy thoughts – not out loud, anyway. Instead, being a smart New York journalist, she has written Wedding Toasts I’ll Never Give, her witty take on marriage – her own and other people’s. It takes the form of a memoir that leaps about in time, topic and tone.

Her book is not a guide, but it offers guidance. With marriage, you have to suck it and see; if it sucks, you may not want to see it through. Ada, 41, married at an “immature” 19 so that Nick, her Canadian boyfriend, could work in the US but, gradually realising that his feet were fidgeting, she threw him out. “A couple of years and several musicians later, I met Neal.”

For Neal, too, it was a second marriage; she was 24, he was 25, which among their New York contemporaries made them feel like a child bride and underage bridegroom. He came with a son, Blake, now away at college, and they live with their other son, Oliver, in a small Brooklyn flat and a house in the Catskills, New York state.

Ada studied Sanskrit at university but decided journalism offered more of a career. Fighting with her husband was the theme of an article she sent to the New York Times and The Wedding Toast I’ll Never Give, became one of the paper’s most popular pieces of the year. Readers wrote in to thank her. “I read it and actually sobbed,” one woman declared. “I really don’t like him much this weekend,” admitted another, about her husband, continuing, “but I love him. Despite the fact that he lost the key to the wine fridge.” “Thank you so much. You pretty much just saved my marriage this morning,” stated another, who planned to keep the piece at hand for future moments of discord.

The article was the basis of this short, sharp and sensitive volume.

Ada was on her American publicity tour when I spoke to her on the phone and put to her the question she has been asked most about her book: does Neal take a dim view of his portrayal?

Her husband did have one request: ‘Write that I have a nice penis.’ She duly obliged

She has revealed that he slurps his coffee and rattles the soup spoon against his teeth. He is a financial walking disaster area. And worse. It is not that she would actually kill him but she has confessed to a friend – and now to us readers – that she sometimes wishes he would just, well, disappear.

“He loves the book and he loves being exposed,” she replies cheerfully. “He’s a musician and performer and he performs naked on stage. He’s an exhibitionist; he’s the perfect person to be married to as a memoirist.”

He did have one request: “Write that I have a nice penis.” She duly obliged, on page 111: “He has a magnificent penis.” And he certainly cannot complain about her wonderful tribute elsewhere: “My life with this man is the best of all possible worlds,” even if she immediately qualified it with, “Sometimes maybe it’s the worst, too, but it’s the only one that’s truly all mine.”

Ada Calhoun and her husband, Neal. Photograph: Courtesy Ada Calhoun

She had whipped through her first wedding in her lunch hour. Her second was more elaborate, featuring as it did both food and guests. “All lovely” is how she remembered the speeches, including an unscheduled poem about taxis delivered by a friend of Neal’s. The kind of toast she would have given, if called on at someone else’s wedding, would have been as welcome to fellow wedding guests as the appearance of the Ancient Mariner with a dead albatross round his neck.

“I’d probably end up saying that even good marriages sometimes involve flinging a remote control at the wall.” She loves weddings and my guess is that fellow guests love her company but a matrimonial celebration is not the time to express her view that “All the couples therapy and communication seminars in the world won’t save you if you aren’t prepared to close your eyes and hug the mainmast through a storm.”

During what she described as “a recent rough patch”, the two of them went back to consult the priest who had married them: “We asked him to remind us, again, why that had been a good idea.” His reply, in so far as I can follow her account, was along the lines of: Good question – lots of other couples can’t answer it either.

Ada went on to pick a lot of other brains, including those of her first husband, who, she discovered, has turned out rather well. Practically all of the couples with decades under their belts admitted that they had considered divorce – and were glad they had stayed together.

‘I made out with someone,’ she once confessed to Neal. ‘I didn’t have sex with him. I really hope you’re not upset’

Her witty, enthusiastic, cautionary, emotional and hard-headed reflections ought to be required reading for anyone entering, experiencing, leaving or avoiding marriage. Or for those who are preparing to knock on the register office door again. Not to mention those of us who as a guest have ever been asked to make a speech about the happy couple and want to avoid putting our big feet in our nervous mouths.

There are many highly personal topics from which a lesser woman than Ada would have steered well clear.

“I made out with someone,” she once confessed to Neal. “I didn’t have sex with him. I really hope you’re not upset.” There was a long pause until he came out with, “I’m not too upset.”

Like her, being married has not stopped him being attractive to the opposite sex. He had a confession of his own, about an event that took place on the very same night when she nearly went the whole hog: “Someone we both know had told him he was attractive and he’d said she was, too.” That’s as far as it went, but, she says, “I was furious. Then I was upset with myself. By doing what I’d done, I’d abandoned the right to be offended.” She was only too aware that she had descended from the moral high ground.

A shrewd observer of herself as well as of other people, she avoids the twin traps of psychobabble and too much information.

“I am not an oversharer,” she assures me. “I am not one of those people who comes up to you at a party and tells you their sexual secrets. In the book, every story is to make a point.” With her friends, she is more open with her secrets: “It would be very hard to blackmail me!”

She is also a sharer to the extent of showing the relevant passages to the friends and relatives she mentions. “Everyone in the book knows they’re in the book.”

Ada was an only child in “a reasonably happy home – Bohemian and eccentric” in Manhattan. Her father is the New Yorker art critic Peter Schjeldahl and her mother, Brooke Alderson, left acting to persue different projects, the latest being “a Rip Van Winkle-themed mini golf course”. The hip – some say hippest – street in New York where Ada grew up features largely in St Marks is Dead, her highly praised first book.

Her parents have celebrated their 43rd wedding anniversary and one can see why. When Neal left home for a while because of his “feelings for another woman,” it was Ada’s father to whom he went for advice, which was: “You could leave, but you would just have different problems.” Neal went back to Ada. During another rocky period, it was Ada’s mother whom she asked: “How do you stay married?” To which Brooke replied: “You don’t get divorced.”

Ada emphasises another marital truth: “Every marriage is different; the fabric is different. There are as many ways to have a marriage as there are marriages.” It is important to remember that there is darkness as well as joy: Instagram does not reflect the nuances of light and shade.

But does a relationship need to be sanctified – or rubber-stamped – by marriage? “I have friends who don’t get married,” replies Ada. “I am certainly not making a judgment.” However, she feels that a wedding brings “more cement” to the party. “I think there is value in the ceremony, a public declaration of commitment. A wedding is a moment of grace, a flicker of beauty.”

What, I ask Ada, would she say if proposing a toast when I get remarried, both of us for the second time?

“How wonderful,” she would tell us. “You’ve been through so much in life and know what you’re doing. It’s beautiful when people who have been round the block make that testimony.”

There was, in fact, one wedding at which she did feel the urge to get on her hind legs, but by this time the toasts were finished, Neal was performing an evocative song by Prince and her moment had passed. In the final pages, she nails her colours to the marital mainmast by putting on paper what she would have said in person.

“I am so happy for you,” she would have declared. “But I am just as happy for all of us here today.” The two people who are joining together in public are also bringing together their two families. “They’re like the pull tab on a zipper, merging the two tribes into one family.” The marriage becomes a joint enterprise for all the witnesses – or shareholders – of the ceremony, who thus have a stake in keeping it in a flourishing state.

Ada’s own mouth has a zipper when it comes to predicting how much happiness any happy couple will clock up: “The couple who endure are not always the ones who are the most compatible or the best behaved.”

How about, for example, that couple to whose marriage both the bridesmaid and Ada gave five years max? “They’ve been together for ever, so happy.”

• Wedding Toasts I’ll Never Give by Ada Calhoun (WW Norton, £12.99). To order a copy for £9.99, go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.