Using a version of these ancient techniques, a past world memory champion named Ben Pridmore was set to prove he had memorized 50,000 digits of pi. (Trumped by a man who recited pi to 83,431 places, Pridmore spent the next six weeks cleaning the images of pi out of his memory palaces.) In joining their ranks, Foer develops various loci, including friends’ houses, his old high school, and Camden Yards. He mentally collects a population of images — often lewd or ridiculous — which he will assign to numbers, playing cards or whatever else he will need to memorize. (Hence his title, which represents the combination of images he uses to remember the four of spades, the king of hearts and the three of diamonds.) In this way, a long string of numbers becomes a farcical tour of fantastical images, distributed in a memory palace. They almost don’t need to be memorized, per se. Once you attend to them, it is hard to forget them. Dom DeLuise hula-hooping plays a pivotal role for Foer, as does an earring-wearing Incredible Hulk on a stationary bike.

Irregular images aside, Foer’s missteps are few. Discussing the neurological underpinnings of memory, he repeats some commonly held myths about it, for instance, that obscure facts — “where I celebrated my seventh birthday” — are “lurking somewhere in my brain, waiting for the right cue to pop back into consciousness.” In fact, not only are many such memories lost for good, even the memories we do have are often quasi-fictionalized reconstructions. Foer inexplicably devotes space to attempting to convince the reader that Daniel Tammet, a renowned savant who memorized 22,514 digits of pi, may not actually be doing it naturally, but only by using the same kind of mnemonic aids used by Foer and his fellow competitors (would it matter?). And at times he seems to have lost some perspective on his endeavor, as when he states, without apparent irony, that the Memory Championship, begun “as a one-day contest” 20 years ago, “has now expanded to fill an entire weekend.”

But Foer is too engaging to put us off. His assemblage of personal mnemonic images is riotous. He makes suspenseful an event animated mostly by the participants’ “dramatic temple massaging.” By book’s end, Foer can boast the ability to memorize the order of nine and one-half decks of cards in an hour. Yet he still loses track of where he left his car keys like the rest of us. He numbly types into his cellphone the phone numbers he does not want to bother to remember. And one can only imagine what he will do with the fantastical images that now people his brain.

We cannot be too disappointed that Foer’s mnemonic immersion did not make him the world’s smartest person. Not everything is equally important to remember. And most things worth remembering are precisely unlike a deck of cards: memories of your own life are spindly, slippery things, interwoven and ever changing. But Foer has given us a hula-hooping Dom DeLuise, and perhaps the fortitude to try memorizing that favorite high school poem again. This time with pictures.