While the mystery (about a poet who stumbles upon a body in a toy shop only to return with the police to discover the body gone and the toy shop nonexistent) is clever enough (think Bryant and May at its most droll), it is decidedly an entertainment, one in which Crispin even breaks the "fourth wall" -- while locked in a closet, Fen speculates on what title Crispin will give this new adventure and comes up with several possibilities that place him in an heroic light.
Crispin, who wrote his first Fen mystery while he was still an undergraduate at Oxford, is so funny and so fey that one expects his novels to offer guest appearances by Bertie Wooster and his valet Jeeves. While he was a composer (he did music for the Carry On series, written under his real name Bruce Montgomery), book editor and crime fiction reviewer for the Sunday Times, it is for the Fen books that he is most remembered.
There are a total of nine delightful Gervase Fen novels and several dozen short stories. Felony and Mayhem Press has reissued six in the series so far, but The Moving Toyshop remains among the missing. Still, you can find it in some shops who have imported it (it is published by Vintage, a British imprint of Random House). It may not be a Christmas story but it certainly is a holiday treat.