[2] Christie's Superintendent Battle has a cameo appearance at the end, but plays no part in either the solution of the mystery or the apprehension of the criminal.
[2] The novel concerns the efforts of a retired police officer, Luke Fitzwilliam, to discover the identity of a serial killer active in the village of Wychwood under Ashe.
He learns that the series of deaths were mistaken for accidents by the locals, while the nobleman Lord Whitfield mysteriously attributes most of them to divine justice.
Upon his return to England after his overseas job in the police, Luke Fitzwilliam shares a London-bound train carriage with Lavinia Pinkerton.
He lists all the murdered locals and their offence: Mrs Horton had argued with him, Tommy Pierce did mocking impressions of him, Harry Carter shouted at him while drunk, Amy Gibbs was impertinent to him, Humbleby disagreed with him on the village water supply, and Rivers used his car without permission and then spoke disrespectfully to him.
Bridget decides to stay at Honoria Waynflete's house, after asking Luke to tell her exactly what Miss Pinkerton told him.
After a brief meeting with Mrs Humbleby, the doctor’s widow, Luke realises that Honoria may well be the murderer and runs to rescue Bridget.
The Times Literary Supplement of 10 June 1939 published a review of the book by Maurice Percy Ashley, together with And Death Came Too by Richard Hull which began "A week in which new novels by Mr Hull and Mrs Christie appear should be a red letter week for connoisseurs of detective fiction.
After considering in isolation And Death Came Too, Ashley turned his attention to Murder Is Easy and started, "Mrs Christie has abandoned M. Hercule Poirot in her new novel, but it must be confessed that his understudy, Luke Fitzwilliam, a retired policeman from the Mayang States is singularly lacking in 'little grey matter.'
After outlining the basics of the plot and the romantic interests of the main character, Mr Ashley concluded, "He (Luke) is less effective a detective than as a lover, which is not surprising since neither he nor the reader is provided with any clear clues pointing to the fantastically successful murderer.
The love interest scarcely compensates for the paucity of detection and the characters verge on caricature; nor is Fitzwilliam able to recapture vividly enough the circumstances of the earlier murders.
"[7] Mary Dell of the Daily Mirror, wrote on 8 June 1939, "It'll keep you guessing will this latest book from the pen of one of the best thriller writers ever.
"[8] An unnamed reviewer in the Toronto Daily Star of 2 December 1939 said, "An anemic thread of romance threatens to sever on occasion but the mystery is satisfying and full of suspense.
The UK serialisation was in twenty-three parts in the Daily Express from Tuesday, 10 January, to Friday, 3 February 1939, as Easy to Kill.
[11] Adapted into a television film in the United States in 1982 with Bill Bixby (Luke), Lesley-Anne Down (Bridget), Olivia de Havilland (Honoria) and Helen Hayes (Lavinia).
Adapted for stage by Clive Exton, directed by Wyn Jones, and performed at the Duke of York's Theatre, London (23 February - 10 April 1993), starring Charlotte Attenborough, Peter Capaldi, Nigel Davenport, Irene Sutcliffe and Ian Thompson.
New subplots were introduced, and the murderer's motive was changed: A BBC Radio 4 adaptation in three parts by Joy Wilkinson and directed by Mary Peate, with Patrick Baladi as Luke Fitzwilliam, Lydia Leonard as Bridget Conway, Michael Cochrane as Lord Whitfield, Marcia Warren as Honoria Waynflete, Marlene Sidaway as Miss Pinkerton and Patrick Brennan as Billy Bones/Rivers.
The novel was adapted as a 2015 episode of the French television series Les Petits Meurtres d'Agatha Christie.
[13] The cast includes David Jonsson as Fitzwilliam, along with Morfydd Clark, Penelope Wilton, Sinead Matthews, Tom Riley, Douglas Henshall, Mathew Baynton and Mark Bonnar.