It may be a short subway ride to Long Island City from Manhattan, but P.S.1, the nation’s oldest nonprofit art space, can seem a world apart from Chelsea and Museum Mile. What begins as a difference of architecture — P.S.1’s converted former schoolhouse feels at once more intimate and haphazard than the rigid spaces of whitecube galleries and mega-museums — quickly becomes one of attitude. If the contemporary art scene in Manhattan often seems either dauntingly inaccessible or patronizing in the way an institution practically holds your hand through an exhibition, P.S.1 has a fluid interior structure and few didactic texts. No one tells you how to proceed through the galleries or what to think of the art. You are free to wander, encouraged to explore on your own. As a result, the experience feels less about prestige or money and more about the simple joy of discovery.

The best of the museum’s current suite of exhibitions, most of which opened February 11, is in keeping with this sensibility. “Not for Sale” features contemporary works that for one reason or another have never been offered to the art market. The pieces are generally accompanied by a brief artist’s statement explaining the withholding — explanations that, like the works themselves, range from sincere and sentimental to paradoxical, ironic, and even nonsensical.

Sarah Sze’s 1997 installation contains neatly ordered objects from her studio — sneakers, a ladder, used coffee cups, sweatshirts, lots of sweets (Bazookas, Starburst, Hershey’s Kisses, Fruit Loops), and much much more — that constitute a kind of self-portrait. When it was made, the work represented a breakthrough for the artist, allowing her to see “objects as evidence of behavior.” But she never sold it for a more practical reason: It would have meant giving up “my furniture, sneakers, and most importantly, my books,” she writes. If this explanation strikes us as perfectly earnest, Glenn Ligon is clearly up to conceptual games when he describes why he held onto his “Condition Report” (1997). The work is actually a diagram of a 1988 painting by the artist that contains notes from a conservator describing restoration issues. Mr. Ligon claims that he never sold the “report” in order to protect the conservator, whose regular employer forbade him from working for private clients. But did he restore the painting? We are never told.

As fun as the art is — and there are excellent works by Janine Antoni, Luis Gispert, Jasper Johns, Stephen Shore, and Richard Tuttle, among many others — these idiosyncratic artist statements are the true joy of the show. Some fail to disclose much of anything — for example, Alex Katz tells us that he keeps his portrait of actress Kate Valk because it occupies a wall in his studio and he has nothing to replace it with — and yet they still offer insight into an artist’s personality. Strolling through the galleries, you begin to understand that the financial exchange between artist and collector is substituted by this personal exchange between artist and viewer. The artist’s words have replaced the price on the label.

If none of the other exhibitions at P.S.1 are as consistently exciting as “Not for Sale,” they all offer distinct pleasures. Take, for example, the mini-survey of the inventive photographer Vik Muniz. Whereas most artists have a signature style, Mr. Muniz has a signature concept. He uses commonplace materials — dust, ink, chocolate syrup, trash, and toy soldiers, to name a few — to design recognizable images, ranging from classics of art history to excerpts of popular culture, and photographs the results. Even when you know they are coming, his tricks are still able to mesmerize.

The bewildering premise for the group show “Silicone Valley” is the similarity between the words “silicon” and “silicone,” which somehow relates to issues of surface illusion and the grotesque. My advice: Don’t puzzle too long over this muddled concept; just enjoy the art. Highlights include Peter Caine’s mechanized, Lycra-embalmed totems, Marlene McCarty’s psychologically fraught drawings, Catherine Ross’s digital video of frantic hand gestures, and William Pope.L’s antic trophy room, where stuffed animals slathered in preservative-saturated condiments such as peanut butter and mayonnaise hang from the wall like hunting prizes.

And there is more — the first American exhibition of Norwegian photographer Tom Sandberg, a small show dedicated to avantgarde filmmaker Jonas Mekas, the organic “Emergency Room” that changes everyday at 12:30 p.m. in response to the news cycle, and several smaller projects tucked away in corners and unoccupied spaces of the museum. These everchanging installations, which you often stumble upon even if you do not seek them out, are a highlight of any visit to P.S.1. My current favorite is Katrín Sigurdardóttir’s “High Plane V” (2006). You begin in a room that is empty except for two ladders, but climb to the top and poke your head through the hole in the ceiling, and you’ll see a vast icescape, a flat white expanse punctured by the occasional jutting iceberg. If someone has climbed the other ladder, his or her face also becomes part of the vista. Viewing this other person’s head, which breaks the plane of the horizon like a rising sun, it suddenly dawns on you that you, too, have brought the work to life — by simply bringing life to the work.

“Not for Sale” until April 16; Muniz until May 7; “Silicone Valley” until April 9; Sandberg until April 16; Mekas until April 16; “Emergency Room” until March 19; “High Plane V” until May 7 (22-25 Jackson Ave. at 46th Avenue in Queens, 718-784-2084).