LONDON — Nostalgia ain't what it used to be.

In these frenzied, media-saturated times, the lure of a simpler past is more powerful than ever.

That may explain the success of "The Dangerous Book for Boys," a deliberately retro tome that's the publishing sensation of the year in Britain. It was released May 1 in the U.S. and shot to No. 5 on Publishers Weekly's best-seller list.

Exuding the brisk breeziness of Boy Scout manuals and Boy's Own annuals, "The Dangerous Book" is a childhood how-to guide that covers everything from paper airplanes to go-carts, skipping stones to skinning a rabbit.

It spent months on British best-seller lists, has sold more than half a million copies and took the book of the year prize at the British Book Awards in March.

Now American boys — but not their sisters — can learn how to play marbles, make invisible ink, send Morse code and build a tree fort.

"I wanted to do the kind of book that we had lusted after when we were kids," said Conn Iggulden, who co-wrote the book with his younger brother, Hal.

"My dad was born in 1923 and his father was born in 1850, and we had some old books in the house with titles like 'Chemical Amusements and Experiments' and 'Fun With Gunpowder.' The thing we didn't have was a single compendium of everything we wanted to do. I remember endlessly looking through these (books), generally to find things that I could make explode or set on fire."

A big, affable, dark-haired thirtysomething who writes best-selling historical novels about the exploits of Julius Caesar and Genghis Khan, Iggulden exudes boyish enthusiasm.

He and Hal, a theater director, researched the "Dangerous Book" over six months in a garden shed, rediscovering the lost childhood arts of secret codes and water bombs and building simple batteries and pinhole projectors.

"Rule No. 1 was we either had to make it or do it — we've both read books where the author clearly hasn't made a raft or whatever, and so the instructions don't work," Iggulden said. "That meant we had to play marbles ... and skin a rabbit. A little bit grisly, that one. But then, we did make it into a stew, and we did eat it.

"It was not a great stew," he admitted. "It was pretty rubbery."

Some parents may balk at encouraging their offspring to skin a rabbit — or tan a hide, another skill imparted by the Iggulden brothers.

Conn Iggulden argues that "if you spend your life going to supermarkets, you should know where the meat comes from, and exactly what's gone into it for your eating pleasure. I think that's worth doing once for just about anybody."

Sales figures suggest the "Dangerous Book" has struck a strong chord among adults concerned about the increasingly sedentary, regulated lives of today's children — a society with computers in every classroom but often without climbing equipment in the playground.

Susan Watt, the book's publisher at HarperCollins, said its appeal lies in the fact that it is "a celebration as much as a how-to book."

"They're celebrating a romantic vision of their boyhood," she said.

"I also felt it has, from both the authors, a unique and genuine voice. This is nothing contrived and you can feel that. Their hearts were in everything they wrote and they enjoyed everything they wrote."

Some elements of the book have been changed for the U.S. edition. Cricket is out and stickball is in; the history of the British empire has been replaced by accounts of the Alamo and Gettysburg.

But its essence remains. There's an old-fashioned, improving tone to the book, with its chapters on famous battles and true tales of courage, its Latin phrases and rules of grammar, and "seven poems every boy should know."

"I don't think it is particularly old-fashioned," Iggulden said. "I think the reason people think it is old-fashioned is that it's optimistic, and an awful lot of modern books tend to be fairly cynical in their outlook — postmodern, tongue-in-cheek.

"I thought, I want to write it straight and I want to write it optimistically, because that's what childhood is about. You don't have any doors shut in your face. You can be absolutely anything, you can be interested in anything."

It's possible to see a less wholesome side to the book's nostalgia. Girls are discussed, in a single chapter, as something akin to another species: "They think and act rather differently to you, but without them, life would be one long football locker room. Treat them with respect."

Girls are explicitly — and, some argue, unnecessarily — excluded by the book's title.

Iggulden is unconcerned.

"It's not exactly that we are excluding girls, but we wanted to celebrate boys, because nobody has been doing it for a long while," he said.

"I think we've come through the period when we said boys and girls were exactly the same, because they're not. Boys and girls have different interests, different ways of learning, and there's no real problem in writing a book that plays to that, and says, let's celebrate it."

Already, for good or ill, the Iggulden brothers have sparked a mini-boom in gender-specific publishing. Pocket versions of the "Dangerous Book" and a desk diary are planned. Meanwhile, Penguin is issuing "The Great Big Glorious Book for Girls," billed as a book for women who "dream of making elderflower cordial and need reminding of how to play cat's cradle."

Some might say the girls have drawn the short straw here.