It's often controversial, and when it's not it's often met instead with complete indifference. It's usually expensive � and generally funded from the public purse. It's public art, it's coming to a town near you, and you probably don't have much say in how it's going to happen.

Thankfully, a younger generation of artists, architects and planners � aided by entrepreneurs - are pulling apart the older model of public art projects and raising standards as they do. Two new titles look at what seem like very different approaches to art in public spaces.

New Public Spaces features massive regeneration projects; civic squares, urban parks, community buildings and pedestrian precincts. Street Renegades, meanwhile, looks at the way that artists have been intervening in the urban environment.

It's more than graffiti � Street Renegades is subtitled 'new underground art'. While traditional graffiti artists are interested in getting their name up in the biggest letters possible, the artists featured here want to carry out interventions in the streets that make their audience stop and look, question and wonder.

London artist Eine, for example, has written single letters on shop security shutters. The shutters are grim and gritty, often raising fear of crime in their neighbourhoods; Eine's use of a colourful, circus-style typeface lifts the spirits.

Similarly, Jorge Rodriguez-Gerada's giant charcoal drawings, portraits the size of the side of houses, can only be seen as adding to the urban environment. And street art collective Knitta, covering street furniture and trees in knitted wrappings; or Samuel Francis, who paints derelict buildings and bunkers in bright colours, must raise a smile wherever they work.

Many of the projects in New Public Spaces are created with the same mix of wit and wonder.

Take Thomas Heatherwick's Rolling Bridge for Paddington Basin, which curls into a sculptural snail-shape when not in use. Or the giant seesaw benches in Tilla Durieux Park in Berlin. Or the Maritime Youth Centre in Copenhagen, whose roof doubles as a skatepark and urban playground. Give the artists in Street Renegades a budget and a team of planning professionals, and they might come up with some similar ideas.

Of course, many of the projects in New Public Spaces are at the cutting edge of architectural practice, pushing the potential of public space to its maximum. Muir Island, floating on a river in Austria, is a magnificent organic shape, a space-age ship, creating a new type of public space � a palace in midstream.

Westblaak Skatepark reclaims a sprawling traffic island, turning it into an urban sports centre and a popular park.

Thomas Heatherwick's Blue Carpet connects a number of neglected spaces in Newcastle city centre, creating one new space and playfully reclaiming it, making an almost domestic space. Sections of the carpet are literally rolled back to form benches, curled up to allow trees to burst through. This project, funded by Arts Council England, was key to Newcastle's renaissance.

Not every project in New Public Spaces is on a massive scale though. Guerilla gardeners from the Toronto Public Space Committee are transforming small, neglected corners of their city. Signs from a CABE promotional campaign are urging people to 'Walk On The Grass'. And designer Clare Cunningham is turning dumped shopping trolleys into colourful planters.

All of these smaller projects could feature just as well in Street Renegades. Proving, perhaps, that everyone wants to play in the urban playground - and the line between anarchic art and architecture is a very fine one.

New Public Spaces by Sarah Gaventa is published by Mitchell Beazley, supported by CABE Space, ISBN 1 84533 134 6.

Street Renegades by Francesca Gavin is published by Laurence King, ISBN 978 1 85669 529 9.