Once, the spraycan "kings" of New York's subways astounded the world with their exuberant graffiti images. Now a new generation of artists has hit the streets and is decorating neighbourhood walls with memorials to the tragic and untimely deaths of friends and loved ones. "R.I.P." - assembling the very best of a vibrant street art wave - contains colour photographs of memorials from Harlem and the Lower East Side, the South Bronx and Brooklyn, as well as the moving stories behind them. The victims of shootings, accidents, arguments, police killings and drug-related turf wars may be gone, but thanks to these paintings they are not forgotten: for a violent and indifferent city has also spawned a rich urban art form. Martha Cooper's first book of photographs was "Subway Art" (with Henry Chalfant, Thames and Hudson, 1984).