The Cottingley Cuckoo is an urban fantasy and horror novel by A. J. Elwood, pen name of English writer Alison Littlewood.

At the time, Conan Doyle had recently published photographs that cousins Frances Griffiths and Elsie Wright had allegedly taken of fairies in Cottingley.

In these letters, Fenton reveals the true nature of fairies, that they are not pretty little winged people, but are the dangerous and vindictive creatures from folklore.

Her mother was later found to have Capgras Syndrome, and Rose wonders whether Charlotte wrote those letters herself in an attempt to explain what had happened to her.

The novella is a collection of letters written by Lawrence Fenton in the early 1920s to Arthur Conan Doyle and Edward Gardner.

[2][3] Littlewood said that after the novella was published, she began to wonder how a troubled person today, vulnerable and open to suggestion, would react to those letters from the past.

[2] Littlewood added that The Cottingley Cuckoo "is [all] about belief – why people choose to believe the things they do, and if, once they've begun, they can turn back.

The central character, Rose, is "sympathetic[ly] and carefully drawn", while Mrs Favell is depicted as "a mysterious ... intruding time traveller" and "breathtakingly cruel".

[3] Wilkes stated that Rose's escalating nightmare towards the end of the book is "the sort of dénouement which is tricky to pull off", but here Elwood has executed it "successfully".

Wilkes found The Cottingley Cuckoo "deeply chilling" and recommended it to readers interested in "literary supernatural horror".

[6] Deeming stated that Rose is underdeveloped, making the character difficult to empathise with, and said she did not enjoy Elwood's literary style, in particular the book's ambiguous ending, which she felt "just didn't work for me".