Changing Pages, York City Art Gallery, until January 28

When is a book not a book? When it is a piece of cheese, a bar of soap, a dishwasher or a cooking pan.

No, your reviewer has not been at the Christmas sherry, but looking at Changing Pages, the Collins Gallery Touring Exhibition of British and American Moveable and Pop-Up Books.

After the clattering chatter of automata arrested the ears in the Devious Devices show, here's another where the eyes are not the only sense to be tantalised.

Enter the upstairs gallery and you are struck by the smell: the scent of paper and books (although the Damien Hirst book disappointingly does not have a formaldehyde whiff!).

The eyes are put to the test too in a somewhat cluttered exhibition with no centre of gravity, the white-walled room becoming as much an Aladdin's Cave and a library as a gallery. With much of the pleasure lying in wait in the delicate detail, the knees are in constant use too, for crouching, even kneeling, to look through peep-show keyholes or read writing.

Hands are used regularly, albeit that several exhibits carry the request Please Do Not Touch, a somewhat ironic stricture in the tactile land of the pop-up book. Others ask that you handle them with care; others demand to be pulled out, flipped over, popped-up and even sniffed.

So far, the content of this review might suggest this is a children's exhibition, and while the third-age viewer might feel the up-down challenge makes it akin to an assault course, adults will savour it as much, if not more, than children.

With more than 200 books from the last 20 years on display, Changing Pages lives up to its title by looking at the creative ingenuity behind both the artist-made and mass-produced moveable and pop-up book.

Paper engineering - and what a lovely combination of art and science that term conjures - first became established in books in the 19th century, represented here by the works of Lothar Meggendorfer and Ernest Nister. The pace of change has been most rapid in recent years, hence the sheer diversity of materials now used and on show.

You may need to visit this show more than once to appreciate fully that diversity, particular the "one-of-a-kind" books - pieces of art in book form - such as Natalie Farmer's peep-show theatre, the brittle feminist wit of Deborah Phillips Chodoff, the tunnel books of Edward Hutchins and Lee Suffey's disturbing observations of life in an institute for the mentally ill.

This alternative edition of Top Of The Pops is well worth popping up to see, smell and scratch.