Obtaining legitimate copies of classic detective fiction ebooks is difficult. Very few big-hitting authors have allowed their works to drift into the public domain, and while the promise of Google Books and Project Gutenberg to make out of copyright ebooks available for free is alluring, the reality is that very few stone-cold classics are legally available.

There are gems hidden in the rough. Sure, the majority of Conan-Doyle’s Holmes output is legally available, and you might stumble across the odd GK Chesterton, but sifting the wheat from the chaff can be a laborious process.

So we’ve done it for you.

What follows are five of our favourite classic detective fiction reads that are often overlooked but are freely available. Of course the latest Ian Rankin isn’t available for free, and given the genre’s relative youth few twentieth-century classics are available, if at all. But there are overlooked charms from some of the genre’s most famous practitioners. So we find an early Agatha Christie, two blueprints of Golden Age writing, and a smart story from a surprising author. We hope you enjoy reading these as much as we enjoyed looking for them – and be sure to use the comments and Twitter to let us know about any classics you’ve caught that we’ve missed!

The Moonstone – Wilkie Collins
We have to admit that it had been a while since we read Wilkie Collins’ revered 1868 novel. But armed with a digital copy and a dusty study guide dug out from undergraduate days, we once again appreciate the true greatness of this Victorian epistolary. The story exhibits what have become established conventions in the crime and detective fiction genre – from gentleman detective Franklin Blake, to the country house setting and inept local police force.

Collins drew on his legal training and employed several narratives to create suspense and drama, throwing in red herrings and twists, and constructing the first ‘locked room’ novel in an effort to encourage the reader to piece together the plot from multiple accounts. Above all else, however, The Moonstone is a brilliantly plotted read, and the framework for all Golden Age crime fiction that followed.

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The Murders in Rue Morgue – Edgar Allen Poe
Wilkie Collins may have constructed the first crime fiction novel, but Poe’s short stories introduced the first procedural narrative and detective in C Auguste Dupin, an amateur sleuth with a rational, scientific mind.

After the brutal murder of a mother and daughter, Dupin and his narrator accomplice – an influence on Conan-Doyle no doubt – embark on a series of interviews and investigations, none of which corroborate. Dupin, the narrator and the reader are presented with multiple accounts of the same crime, and so begins a process of elimination until the truth is revealed.

The Murders in Rue Morgue is a short, precise account of how the author assumes a murder investigation is undertaken, and the problems investigators encounter. It proved to be furtive ground for generations of crime fiction writers to further plough.

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The Great Impersonation – E Phillips Oppenheim
Oppenheim merits a place on this list for the simple reasons that he is hugely underrated and under-read. His novels – there are over 100 – mix crime fiction with espionage. The Great Impersonation is a fascinating and entertaining mix of both, and a precursor to both the Bourne series and Stieg Larsson.

The plot begins in pre-WWI Africa, where a German spy plans to assassinate then assume the identity of a prominent British gentleman who has been expatriated for more than a decade, then return to the UK looking to influence events in the impending world war. Rather than ‘whodunit’, Oppenheim weaves a tale of ‘whoisit’ and deploys all the hallmark twists and turns we now expect in a novel of this type.

Oppenheim’s writing hasn’t aged well, it must be said, and his characters can appear hackneyed and, at times, offensive. And while it doesn’t excuse them, his plotting and closing reveal helps make up for such deficiencies.

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The Secret Adversary – Agatha Christie
This gripping tale of international espionage told in Christie’s trademark style is often disregarded in comparison to Poirot, Marple and the author’s more famous outings. Yet it features all of the properties that we expect from the Golden Age author, together with some fantastic characters and twists.

Its chief protagonists are Tommy and Tuppence, the least famous but most adventurous of Christie’s investigative characters. It also features another outing for Inspector Japp, introduced two years earlier in the first Poirot novel. Tommy and Tuppence become embroiled in the hunt for a potentially world-changing document, smuggled from the deck of the sinking Lusitania. With a typical case of mistaken identity, red herrings along the way, and twists in the tail, Christie shows how the tea rooms of London hide a more sinister side of the city. It’s classic Agatha Christie from start to finish, with a cracker of a reveal at the novel’s close.

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The Red House Mystery – AA Milne
You might think AA Milne, the creator of Winnie-the-Pooh, may sit a little out of place on a site like CFL. But Milne also produced one ‘locked room’ crime fiction novel, and it is a masterpiece of suspense and intellectual puzzlement.

The plot is pretty straightforward: a dinner party at a grand country house is interrupted by the return of the family’s black sheep, who after a revelatory quarrel is found dead, shot in the head. The chief investigator and his side-kick set about interrogating the guests and staff, and leads, red herrings and motives mount.

Milne’s writing is very genteel, and in places comedic. His characters are drawn from the stiff upper lip brigade, polite maids or the chivalrous footman, and leave little impression. But as a locked room puzzle it is very good, with a rational approach to sifting through evidence and forming a complete picture of how the crime took place and why a man was murdered.

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For more free classics, see our more recent article here.