Two ambitious volumes of interviews with artists have just been published. They are similar, but different. The first is by Richard Cork, a veteran with a Cambridge education who enjoyed a distinguished stint as art critic at the Times. He is nicely old school: chatty and avuncular. The second is by Hans Ulrich Obrist of London’s Serpentine Gallery, ageing Swiss boy wonder of the art fair circuit with a head like a pink dome-nut.