He's the ultimate ex-husband -- irritating in every possible way. You know he's angry, but he acts nicey-nicey instead. When he strains to hide the bitterness, his voice gets even more nasal, as though his sinuses are tightening way inside his head. His smile grows huge.

"In my heart I have disconnected from Sonny & Cher," says Sonny Bono, "and I feel great about that."

But wait ... he seems tired, downtrodden, slightly depressed. The poor guy. Imagine talking about your ex-wife -- who left you in the dust big time -- in five major U.S. cities. He's got a book now, "And the Beat Goes On," which is mostly about their time together. He may still be the mayor of Palm Springs, but you can't help feeling sort of bad for him -- Cher's so famous, so hip, she's got all those cute guys, and there he is ... with his nasal voice, his forced niceness, his gigantic capped teeth. The heartbeat goes on. He's still the same old Sonny. Emphasis on old. What long teeth! His lips have some trouble.

"What's with his mouth?" somebody asked while watching him on CNN Tuesday night. "His teeth are impeding his speech." Larry King had him on the show. And King's mighty lower teeth seemed to be warring with Bono's uppers.

A caller complained: "Sonny, I believe you are bad-mouthing Cher, putting her down."

"I'm sorry you feel that way," Bono answered -- with ear-piercing nasality. "Everybody's got the right to express their feelings."

His mustache is grayer now, the color of old milk. Sheared down to the nubs, it opens to sip an espresso at the Four Seasons. For teatime in the garden court, Bono wears a summer herringbone suit, a white shirt, a bold-print Nicole Miller tie. His gold watch is so big it looks like a naval instrument. His 28-year-old wife, Mary, and their two children are upstairs in their hotel room.

It's true, sometimes he hesitates when he speaks, but it's not his teeth. It's as though a dry desert wind is blowing through his brain ...

When they met five million years ago, Cher had a foul mouth, bad skin, the gaze of a sphinx. She had "eyes as deep and as dark as tunnels." He was 26. She was a 10th-grade dropout, a runaway, but full of Hollywood dreams. "A hot-blooded paradox," he writes. She was 16, and, according to Bono, she had already slept with Warren Beatty.

"I knew from Chastity and other people that {Cher} was real curious about the book," he says now. "That part of our life was not exposed. ... She's not pleased, I'm sure."

The book festered in him for years -- 16 since Cher left him -- then he dictated his memories into a tape recorder so they could be structured by Todd Gold. ("He was the second writer," says Bono. "The first writer was too bitter.")

After many interviews, Gold captured perfectly the language and flaky wisdom of the Sonny Bono Mind-Set: "What a letdown." "She split." "What a buzz." "My dad freaked." "The song bombed big-time."

And Gold captured the braggadocio. Bono first laid eyes on Cher at an Italian restaurant in Hollywood ... "a low-lit joint, I walked into Aldo's like a gunslinger coolly sauntering into a bar."

Bono was being set up with Cher's friend Melissa. After a double date, the girls took the guys to a lesbian bar. Cher and Melissa danced together. "An uneasiness crept over me," Bono writes. His dreams of Melissa were dashed. It was clear she wasn't interested in him. Cher, he writes, "was unreadable," although she insisted later: "I'm not that way."

Hmmm. Was Bono trying to imply that Cher was a lesbian before they met?

"No, not at all," he says sheepishly. "Just that she was this waif searching in Hollywood. I was a waif too."

He does, straightforwardly, say that sex with Cher was never fabulous: "No fireworks."

"Maybe her other relationships were different," he writes. "But it never really meshed with us. In the most intimate moments, Cher was reserved and protective. There was a part of her -- and it still exists -- that no one can get to."

Ambition, which they did share, was steamy instead. Way before she ever dreamed of being a singer, Cher used to stand in front of the mirror and practice signing autographs for fans. Sometimes she'd practice turning them down. Her drive, according to Bono, came from her mother -- a prowling Hollywood extra, a glamorpuss. "Her entire wardrobe," Bono writes, "was geared for after 6."

At first, her publicist said Cher hadn't read Bono's book, that she'd never gotten a copy. Then, last week, her publicist said she'd "skimmed it." Two official responses from Cher were offered. They should be read aloud, deadpan:

1. "I think he should stick to writing songs. He does that better."

2. "Of all the people who have known me well, Sonny knew me the least."

What He Hates Most Sometimes he reads profiles of his famous ex-wife. She gets so much press! All these years, she's gotten to tell her side of things. Sometimes she's asked, "What was the happiest time in your life?"

And she always says the same thing: "When I left Sonny."

The Ringo of Sonny & Cher He wasn't always the whiniest cuckold on the planet. Twenty years ago, he dressed up like Santa's elves and village idiots and let us laugh at him. Then, he took all the shots. He was the Ringo of Sonny & Cher. He was the toad who had a tall, tawny, smart-alec half-breed wife with high manners and high cheekbones. He was the foil on the "Sonny & Cher Comedy Hour." He was the man who happily wrote himself the hit solo "Laugh at Me."

Now he's 56 years old. He became a Republican in 1984. He's been married three more times. He's written 10 Top Ten songs. He appeared in "Airplane II." He appeared on "Love Boat" five times. "It's part of why I quit show business," he says, "sitting around in that trailer, waiting to go on that show."

He's bought two houses from Tony Curtis. He has four children. One before Cher. One with Cher. Two after Cher. (In order: Christy, Chastity, Chesare, Chianna.) Cher caught him having sex with his secretary once. (She didn't do anything about it.) He's been mayor of Palm Springs for one term. He's had a house in the California desert for 17 years.

Twelve chapters (four-fifths) of "And the Beat Goes On" are devoted to Bono's 11 years with Cher. How they met ... how she moved in with him ... how they communicated by reading each other's diary entries ...

How they weren't really legally married until Chastity was a toddler. (Cher's idea: They performed their own makeshift wedding ceremony in the bathroom one day.) How they developed their act. (Songs and put-downs.) How they redid themselves. (They both had nose jobs after their first big hit in 1965, "I Got You, Babe," and Cher had "her breasts reshaped and firmed up.") How they stupidly bought two enormous houses they couldn't afford. (Cher furnished their 54-room Holmby Hills house in three days. "I don't think anyone ever sat in the living room," writes Bono.)

And finally, it's about how Cher hated sharing the spotlight with him. "She really wanted to be bigger than Dylan and Jagger," says Bono. How she ignored him. She was always "absorbed in needlepoint. She was bored. Disinterested."

In November 1972 -- the second year of their hit show -- Cher kicked Bono out of their Vegas hotel room one night. She didn't want to sleep with him. She wanted to sleep with Bill Hamm, their band's young guitarist, instead.

"With a final look at Cher, I turned and walked out of the room," he writes. "No yelling. No slamming the door. I was a zombie who'd been defeated."

They kept doing the TV show for another year. They kept living together in the 54-room house. Cher kept seeing Hamm, then keyboard player David Paich, then Elton John's lyricist, Bernie Taupin, then record and movie producer David Geffen.

Bono had his own lover move in, Connie Foreman, a cigarette girl from Pip's.

Bono blames Geffen for the Wow Finish. Geffen, according to Bono, encouraged Cher to divorce him, to break their TV contract, to start her own solo career. (She signed for her own show -- "The Cher Comedy Hour" -- immediately.) Geffen was "orchestrating Sonny and Cher's demise like a ruthless takeover artist."

In divorce court, Cher charged Bono with subjecting her to "involuntary servitude."

"I recoiled in shock," Bono writes. "Cher's charge was a callously legal way of saying that she had been my slave. Not my wife, my lover, my best friend, my inspiration, or the mother of our child, but my slave!"

There are two brief chapters at the book's end, chronicling the last 16 years of his life -- the 13-week failure of ABC's "Sonny Bono Show," the opening of his restaurant, his one date with Raquel Welch, his appearance in "Hairspray" and his last two marriages.

His wife, Mary, has turned his life around. He has also discovered Dianetics, monogamy and politics. He wants to run against Jerry Brown for a U.S. Senate seat in '92. He has also apologized to his daughters Christy and Chastity for "coming up short" as a father.

Bono and Cher haven't really spoken since the premiere party for "Moonstruck" in 1987, when he and Mary sat at Cher's table at Chasen's in Beverly Hills and she snubbed them.

"We got a real cold reception," he says. "It was real hard. We were sitting at her table. ... I'm sure you've experienced this sort of thing too. You know, when you talk to somebody and you're going, now I wonder what's wrong here?"

The Heartbeat Goes On The book opens with a description of Bono's brief reunion with Cher on the David Letterman show in 1988. Cher had a new movie to promote. Sonny was running for mayor of Palm Springs. Chastity dressed her dad for the occasion, to make sure he looked as cool as her mom.

"Mom's going to dress to kill," Chastity told him. "She'll be awesome. So you'd better have something nice too."

She bought him some baggy pleated black trousers. A silk print shirt. She combed his hair back.

It was difficult to tell what Cher was wearing -- a jacket, and barely anything else. "Her outfit was quadruple homicide," writes Bono. "It personified the difference time had placed between us."

Letterman asked Bono -- not on the air -- about the two tattoos that were visible on Cher's butt. They were post-Sonny butterflies, done in Cher's Gregg Allman phase. But Bono knew all about them. He had seen them, he told Letterman, when Cher would come over to his house and sunbathe nude by his pool ... after the divorce.

Then Bono stood by his former wife, and, well, she looked like ... "a completely different person -- redesigned, remade, redefined. Physically, we were the same two people -- well, mostly the same -- but all those shared emotions and events that had once charged us with passion and urgency were gone."

They sang:

They say we're young and we don't know, we won't find out 'til we grow.

Well I don't know if all that's true, 'cause you got me, and baby, I got you.

Babe,

I got you babe,

I got you babe.

Chastity cried. The audience cried. Mary cried. Cher was oddly unmoved. She seemed "unaffected" by the reunion. "I don't think she cares for those memories," is Bono's explanation. "I think if she could blow them all up, she would."