Typically refers to a multi-layered work, e.g.λ new ads covering old on a roadside sign.
Miraculously, the Stasi's record of Garton Ash's years in Berlin remained intact, and in his extraordinary book The File he recalls going back to Berlin, sifting through the material, and piecing together those years for himself. The result is a palimpsest of memories, observations recorded by informants and agents, and the recollections in his own diaries at that time.