And Then There Were None is one of Agatha Christie's best-known mysteries, widely considered her masterpiece and described by her as the most difficult of her books to have written. Writing for The Times Literary Supplement of 11 November 1939, Maurice Percy Ashley stated, "If her latest story has scarcely any detection in it there is no scarcity of murders... There is a certain feeling of monotony inescapable in the regularity of the deaths which is better suited to a serialized newspaper story than a full-length novel. Yet there is an ingenious problem to solve in naming the murderer," he continued. "It will be an extremely astute reader who guesses correctly."
Many other reviews were also complimentary; in The New York Times Book Review (25 February 1940), Isaac Anderson detailed the set-up of the plot up to the point where "the voice" accuses the ten "guests" of their past crimes or sins, which have all resulted in the deaths of other human beings, and then said, "When you read what happens after that you will not believe it, but you will keep on reading, and as one incredible event is followed by another even more incredible you will still keep on reading. The whole thing is utterly impossible and utterly fascinating. It is the most baffling mystery that Agatha Christie has ever written, and if any other writer has ever surpassed it for sheer puzzlement the name escapes our memory. We are referring, of course, to mysteries that have logical explanations, as this one has. It is a tall story, to be sure, but it could have happened."
Such was the quality of Christie's work on this book that many compared it to her 1926 novel The Murder of Roger Ackroyd. For instance, an unnamed reviewer in the Toronto Daily Star of 16 March 1940 said, "Others have written better mysteries than Agatha Christie, but no one can touch her for ingenious plot and surprise ending. With And Then There Were None... she is at her most ingenious and most surprising... is, indeed, considerably above the standard of her last few works and close to the Roger Ackroyd level."
Other critics laud the use of plot twists and surprise endings. Maurice Richardson wrote a rhapsodic review in The Observer's issue of 5 November 1939 which began, "No wonder Agatha Christie's latest has sent her publishers into a vatic trance. We will refrain, however, from any invidious comparisons with Roger Ackroyd and be content with saying that Ten Little Niggers is one of the very best, most genuinely bewildering Christies yet written. We will also have to refrain from reviewing it thoroughly, as it is so full of shocks that even the mildest revelation would spoil some surprise from somebody, and I am sure that you would rather have your entertainment kept fresh than criticism pure." After stating the set-up of the plot, Richardson concluded, "Story telling and characterisation are right at the top of Mrs Christie's baleful form. Her plot may be highly artificial, but it is neat, brilliantly cunning, soundly constructed, and free from any of those red-herring false trails which sometimes disfigure her work."
Robert Barnard, a recent critic, concurred with the reviews, describing the book as "Suspenseful and menacing detective-story-cum-thriller. The closed setting with the succession of deaths is here taken to its logical conclusion, and the dangers of ludicrousness and sheer reader-disbelief are skillfully avoided. Probably the best-known Christie, and justifiably among the most popular."
The original name of the mystery (Ten Little Niggers) has long been abandoned as offensive in English-speaking countries and a number of others. Some critics have opined that Christie's original title and the setting on "Nigger Island" (later changed to "Indian Island" and "Soldier Island", variously) are perhaps integral to the work. These aspects of the novel, argues Alison Light, "could be relied upon automatically to conjure up a thrilling 'otherness', a place where revelations about the 'dark side' of the English would be appropriate." Unlike novels such as Heart of Darkness, "Christie's location is both more domesticated and privatised, taking for granted the construction of racial fears woven into psychic life as early as the nursery. If her story suggests how easy it is to play upon such fears, it is also a reminder of how intimately tied they are to sources of pleasure and enjoyment."
In the "Binge!" article of Entertainment Weekly Issue #1343-44 (26 December 2014–3 January 2015), the writers picked And Then There Were None as an "EW favorite" on the list of the "Nine Great Christie Novels".