Last Updated on April 22, 2026
September always feels like the perfect month to settle in with a good crime or mystery novel. The long summer days are slipping away, the evenings are getting darker, and there’s something about that shift in the air that makes a suspenseful read all the more satisfying.
Publishers seem to know it too, because this September is packed with brand new titles for fans of crime, thrillers, and whodunits.
Whether you enjoy heart-pounding psychological thrillers, traditional detective mysteries, or the kind of crime fiction that mixes in a little cosy charm, there’s plenty to look forward to.
Some of these books come from well-known authors returning with their latest page-turner, while others are exciting debuts that could well introduce us to the next big name in the genre.
This list brings together ten of the most talked-about new September mystery releases hitting the shelves.
Each one promises twists, suspense, and that irresistible pull of “just one more chapter” that crime and mystery readers know so well.
So, if you’re looking for something new to add to your reading stack, here are ten brand new books worth keeping an eye out for in September 2025.
The Impossible Fortune by Richard Osman
Richard Osman returns with the next instalment of his hugely popular Thursday Murder Club series, The Impossible Fortune, publishing on 25 September 2025.
After a relatively quiet year, the gang find themselves once again drawn into danger. Joyce is caught up in wedding plans, Elizabeth is still processing loss, Ron is facing difficult family matters, and Ibrahim continues to counsel one of his more unusual clients.
But when a guest at Joyce’s wedding confides that they fear for their life, the Club quickly finds themselves investigating a fresh mystery.
What follows involves a kidnapping, a murder, and a villain obsessed with an uncrackable code — perhaps their most perilous case yet.
The Secrets of Secrets by Dan Brown
Dan Brown returns with the sixth installment of his Robert Langdon series, The Secret of Secrets, set to be published on 9 September 2025.
The story starts in Prague, where Langdon attends a lecture by Katherine Solomon, a noetic scientist and his romantic interest, who is about to publish a groundbreaking book on human consciousness.
A brutal murder erupts, Katherine and her manuscript vanish, and Langdon is suddenly pursued by a powerful group and a mythic threat rooted in ancient Prague lore.
His chase propels him across Prague, London, and New York, racing to uncover a secret project that could upend everything we know about the human mind.
A Killer Wedding by Joan O’Leary
Joan O’Leary’s debut novel, A Killer Wedding, is set to publish on 23 September 2025.
It’s a wildly witty, fast‑paced, and wickedly fun mystery that throws you into the midst of billion‑dollar glamour and murder
Christine, a reporter for a top bridal magazine, lands the scoop of a lifetime: covering a high‑society wedding at an Irish castle.
But the event quickly turns deadly when the glamorous matriarch, Gloria Beaufort, is found dead on the first morning of the celebrations
Everyone – from heirs to bridesmaids to the staff – has secrets, and some are deadly. In a setting that feels equal parts Clue and The Devil Wears Prada, this locked‑room whodunit delivers sharp surprises until the final, shocking twist.
Guilty by Definition by Susie Dent
Susie Dent, beloved lexicographer from Countdown, makes her fiction debut with Guilty by Definition, out 30 September 2025 in some editions (including North America).
Set in Oxford’s Clarendon English Dictionary offices, the story follows Martha Thornhill, a senior editor returning home after a decade abroad.
Soon, cryptic letters begin arriving, each laced with coded clues tied to the year her older sister Charlie disappeared.
As Martha and her team unravel the messages, they uncover unsettling secrets, and soon realize someone is desperately trying to pull the lexicographers toward the truth of what really happened all those years ago.
Buried Above Ground by Mike Ripley
Mike Ripley’s Buried Above Ground, set to publish on 2 September 2025, offers a clever and darkly funny twist on the mystery crime genre.
The story focuses on a drama behind the scenes in publishing: Jacon Archer, a mystery‑blogging sleuth, tries to track down reclusive crime writer Duncan Torrens to sort out rights to his backlist.
But as the chase unfolds, from the editor turned librarian to shadowy publishers, murder and secrets quickly surface.
Told through five unreliable voices – the Librarian, the Reader, the Publisher, the Editor, and the Writer – it’s a witty metafictional puzzle that delights in skewering classic mystery tropes while keeping you guessing until the very end.
The Killer Question by Janice Hallett
Janice Hallett’s latest mystery, The Killer Question, arrives on 23 September 2025.
It unfolds in a rural British pub where quiz nights have long been the town’s heart, until a new team sweeps in, crushing the locals with uncanny accuracy.
When a body is discovered in the nearby river, the village’s quiet routine turns deadly.
The story is pieced together through quiz categories, WhatsApp messages, emails, police transcripts, and more culminating in a clever mystery that pulls you into its puzzle.
Sue and Mal, the missing landlords, have a past tied to a secret police operation, and it’s only when their nephew Dominic tries to turn their story into a Netflix documentary that everything comes to light!
Hexes & Hush Money by Hazel Caraway
Ivy Rowan is a charming witch who runs the Catnip Café by the sea, with a purring familiar named Hex.
But her cozy life turns dangerous when a ruthless developer is found murdered behind the café, and the restoration fund disappears with him.
Strange gold coins begin appearing on her tables, and a rival falls victim to a hexed cappuccino.
When Hex is kidnapped, Ivy must solve a century‑old money‑binding spell and unmask a modern killer, or risk her freedom and perhaps her life.
Hexes & Hush Money is a cozy pick full of seaside charm, magical wit, and a dash of danger, and it arrives on 9 September 2025.
Miss Winter in the Library with a Knife by Martin Edwards
Martin Edwards delivers a clever and atmospheric holiday whodunit in Miss Winter in the Library with a Knife, releasing on 11 September 2025 in the UK and early October in the US.
During a snow‑bound Christmas in a remote North Yorkshire village, six down‑on‑their‑luck guests, each linked to crime writing, are invited by the mysterious Midwinter Trust to solve the fictional murder of a crime author for a life‑changing prize.
But when the game turns all too real and death enters the mix, sealed‑off by a storm, tensions rise and the stakes go deadly.
With puzzle‑rich storytelling and a “Cluefinder” to help readers play detective themselves, this is a festive mystery with bite.
A Very Bookish Murder by Dee MacDonald
Dee MacDonald returns to the Scottish Highlands with A Very Bookish Murder, the third heartfelt cozy mystery in her Ally McKinley series, arriving 19 September 2025.
Ally McKinley, a warm-hearted guesthouse owner and accidental detective, hosts a writers’ retreat in the charming village of Locharran.
But the literary fun turns lethal when famed author Jodi Jones is found strangled in the ladies’ bathroom.
Accusations of plagiarism and infidelity ripple through the guest list, turning every attendee into a suspect.
As Ally sifts through torn diary pages and rising tensions, another writer is found dead, raising the stakes.
With her loyal puppy Flora by her side, Ally must untangle trust, betrayal, and literary secrets before the killer slips away—or before she herself is struck off the guest list for good.
The Unfathomable Curse by Courtney Smyth
Courtney Smyth brings us the third installment in The Undetectables series, The Unfathomable Curse, set to be published on 23 September 2025.
This witty, witchy fantasy murder mystery sees Cornelia racing against time after her twin sisters are snatched by the eerie Wickermere Reaper.
As bodies vanish and magical puzzles emerge, Cornelia, along with her friends Mallory, Diana, and Theodore, must return to the seat of the Ghoul Council and uncover deep‑buried family secrets to save her sisters.
Rich in ancient magic, fiendish puzzles, and dark humour, it brings a bold, supernatural twist to cosy mystery for fans of engaging, offbeat sleuthing.
Wrapping Up September 2025 Mysteries
September 2025 is clearly a standout month for crime, thriller, and mystery readers.
The sheer variety on offer means there’s something to suit every taste, whether you enjoy high-stakes globe-spanning puzzles, classic whodunits, or the warmth of a cosy mystery with a touch of humour or magic.
Established favorites like Richard Osman and Dan Brown are sure to dominate the bestseller lists, while debut authors such as Joan O’Leary are adding fresh voices and inventive twists to the genre.
What’s striking about this month’s releases is the balance between the familiar and the new.
Long-running series continue to deliver, offering readers the comfort of returning to beloved characters, while at the same time experimental stories and first-in-series titles promise to expand the boundaries of what crime fiction can be.
For readers, it’s a chance to refresh the to-be-read stack with books that will carry them through autumn evenings.
Whichever of these titles you pick up first, September looks like the perfect time to settle in with a book that keeps you guessing until the very last page.
