Book was published in 1954 and is about a mouse with a name beginning with M who chooses to live at the Boston Museum of Fine Arts and meets all the other animals who pride themselves on being antiquities. They refer to the mouse, disdainfully, as “contemporary”
This is ‘The Contemporary Mouse: A Fable for Art Lovers’ by Patricia Barnard (1954).
The Contemporary Mouse: a Fable for Art Lovers, by Patricia Barnard.
The Contemporary Mouse: a Fable for Art Lovers by Patricia Barnard, published 1954