Who's on first?

We're so used to seeing stand-up comics work alone nowadays that it's hard to remember a "straight man" was once part of a comedy team, not someone who dates women. Indeed, anyone raised on "American Pie" would be surprised to learn that back in the gay old days - when that too meant something else altogether - comedians managed to joke about subjects besides sex.

We're awash in comedy and comedians, but Elizabeth McCracken's latest novel, "Niagara Falls All Over Again," is about a kind of comic relationship that's almost disappeared. Carter and Sharp were born in vaudeville, rose through radio, thrived in B movies, and then passed away in the age of television. Although her duo is purely fictional, the trajectory of their career provides a fascinating description of American entertainment and a tender look at a remarkable friendship.

The opening scene is classic silliness: "It starts with two men - one thin, one fat - dressed in tuxedos, walking down a black-and-white street arm-in-arm. The fat man keeps stumbling. At one point he falls and manages to land on his top hat. The fat man will always land on his top hat, and the thin man will always help him up, whack him over the head, and replace it."

In this case, the fat man is going to marry a horse, but whatever the details - at sea, on the moon, or during war - the basic elements are always the same: another nice mess, madcap antics, a wild chase, high-pitched pleading, and finally their two mugs in a shrinking circle. "Carter and Sharp, briefly the number-one box-office draw in the country ... made 36 movies in 10 years."

The novel comes to us as the late-in-life memoir of Mose Sharp, the thin one, the straight man, the perpetually peeved professor who beats fat Carter through a thousand ridiculous antics. Having spent his life being upstaged by "the funny one," there's real potential here for bitterness, but Sharp is a man of great patience and kindness. Besides, the course of events has more than rebalanced any advantage Carter once enjoyed.

Sharp's theatrical ambitions begin in Des Moines, Iowa. He's the only son among six sisters in a Jewish family. Their father plans to leave his prosperous clothing store to him, but young Sharp and his sister Hattie spend their free time rehearsing dance routines for the stage. When tragedy strikes with an accident ironically similar to the physical comedy that will one day make him famous, Sharp lights out for vaudeville alone.

For two years, he flounders through "two-bit towns with two-bit theaters," doing acrobatics, eccentric dancing, juggling, ventriloquism, and comedy. Finally, he fills in for a missing straight man with Rocky Carter, another two-bit comic wearing a plaid suit that "looked like a worked-over full-color crossword puzzle."

The night of their first performance together, they draw up a contact for the next 30 years, decades of success, wealth, and fame that will far exceed Sharp's fantasies but only confirm Carter's unbounded optimism.

McCracken is a witty writer. She has no trouble creating routines that recall Laurel and Hardy or Abbott and Costello. ("Maybe it doesn't sound funny on the page," Sharp protests needlessly, "but Beethoven on the page is just black dots.") Although he was a professional straight man, as a narrator, Sharp cracks jokes as easily as falling down.

Still, there's nothing zany about this sensitive novel. McCracken understands the ambiguous relationship between comedy and tragedy as well as she understands the relationship between these two funny men. Even a fictional celebrity memoir risks being maudlin, but McCracken knows when to pull back.

For Carter, success feeds a desperate need for love and attention, a gluttony reflected in his burgeoning size. Sharp, as on stage, reacts differently. He finally tames his insatiable sexual appetite and settles down to domestic stability and happiness. Though robbed of the people he loved most, he's learned to live in peace among the silhouettes. But, as in comedy, timing is everything. Their divergent lives make a break in their professional relationship inevitable, but no less painful for either man.

McCracken has a wonderful ear for the way a line or a friendship breaks. There's tragedy in any partnership that cannot or will not change, no matter how funny the enterprise. The setup involves jealousy and devotion, envy and gratitude. At the punch line, you want to laugh and cry.

Ron Charles is the Monitor's book editor. Send e-mail comments to charlesr@csmonitor.com.