Excuse me - Is that seat taken?

The New York subway celebrated its centennial this year, and naturally most of the attention focused on what an immense physical undertaking it was to build. But here comes a volume that celebrates those who ride the trains. Czech-born photographer Peter Peter, now based in New York, found himself in the company of fellow strangers when he took his camera underground to capture candid moments on the train.

It's been said that the first rule of subway riding is don't look at the other riders, just keep to yourself. Over the years that rule has been bent by photographers such as Walker Evans in the 1930s and '40s, whose camera looked passengers directly in the eye to see ordinary people being themselves.

Peter hid his camera in a bag with a small hole to shoot through. His images show subway riders reading, eating, chatting, smooching, but mostly staring into space.

Over two summers of riding and picture-taking, Peter noticed how often life coincided with words and pictures, sometimes with humorous results. Two young girls who might be twins are identically dressed in blue; one of their shirts reads "Lucky," the other, "Love." Each cradles a doll, and then we notice the word "mate" scratched into the train window next to them. A solo passenger's leather coat is open to reveal a Superman "S" on his shirt, while a "Law Enforcement" advertisement on the wall of the train looks over his shoulder.

When his subjects interact with each other, it's as if they were in their own home, oblivious to the public transportation environment around them. A man crochets something large and pink that spills over his lap, while next to him a man yawns, gazing out the window.

There's loads of color in these pictures, softening the gritty image of the New York subway. And of course, since we can't hear the screech and rumble of the underground, we can concentrate on the images: people of all ages, ethnicities, and persuasions.

These are memorable pictures of everyday people we bump past and take little notice of, caught in their daydreams or deep thoughts, a photo album of those who ride the subway and inhabit our most cosmopolitan city, New York.

• Greg Palmer is an assistant news photo editor with the Monitor.