Distinctive, sophisticated, sometimes even weird music! You can hear folk, art/progressive rock, doom... whatever! Very difficult to categorise their stuff, and it's unlikely you've heard anything like that before!
Became to know thier music after a member of Hammill Yahoo Group (a fan group dedicated to Peter Hammill and Van der Graaf Generator music) uploaded a link to their 'Nocturne Fis Moll #4 (Showing Decorum)' clip. Love them since then!;)