Here's a snapshot of what I think is published for the first time in October 2023 (and is usually a UK date but occasionally will be a US or Australian date). 89 titles this month. If I've missed anything or got the date wrong, do please leave a comment.
Please note that, unless specifically mentioned, when a book has differing print and ebook release date, I use the print release date. Translators' names are included where known.
Allen, Jo - Death in Good Time (ebook only) #11 DCI Jude Satterthwaite, Lake DistrictAllingham, Merryn - Murder in a French Village #7 Flora Steele, Sussex, 1955
Armitage, Richard - Geneva
Barron, Stephanie - Jane and the Final Mystery 15 Jane Austen
Black, Tony - The Lock-in #Short Stories
Blackwell, Penny - Murder at the Bonfire #2 Cherrywood Murders
Bond, Martha - Murder in the Library #1 Lottie Sprigg Country House
Bradley, Rebecca - Cold Hard Truth #4 Claudia Nunn
Brett, Simon - Mrs Pargeter's Patio #9 Mrs Pargeter, Gangster's widow
Britton, Anna - Shot in the Dark #1 Detectives Martin & Stern
Brookes, Dawn - The Museum Murders #3 Carlos Jacobi
Brown, Benedict - Murder at Everham Hall #1 Marius Quin, 1920s
Celestin, Ray - Palace of Shadows
Child, Lee (with Andrew Child) - The Secret #28 Jack Reacher, ex MP, USA
Cole, Martina (with Jacqui Rose) - Loyalty
Comley, M A - The Games People Play #21 DI Sara Ramsey
Cordani, Andreina - The Twelve Days of Murder
Cumming, Charles - Kennedy 35 #3 Box 88
Curtis, Emma - The Babysitter
Dalgliesh, J M - A Long Time Dead #1 DI Duncan McAdam, Isle of Skye
Devlin, Cara - Fatal by Design #5 Bow Street Duchess
Ebsworth, David - Blood Among the Threads #1 Wrexham Victorian Mystery
Ellis, Emmy - The Scorched Skin Killer #4 DI Bethany Smith
Forder, Tony J - What Dies Inside Us #11 DI Jimmy Bliss
Gatland, Jack - Counter Attack #4 Tom Marlowe
Giles, Stewart - Danger on the Island #11 DI Liam O'Reilly
Gray, Clio - The Fifth Face of Fear #2 Troubadours
Grayson, C J - Taken While She Slept #1 Detective April Fisher
Greene, Morgan - The Mark Of The Dead #2 DI Jamie Johansson Files
Griffiths, Elly - The Great Deceiver #7 Stephens and Mephisto, Brighton, 1950s
Hall, Emylia - The Harbour Lights Mystery #2 Shell House Detectives, Cornwall
Hall, Lisa - The Day She Disappeared
Hallett, Janice - The Christmas Appeal #2 Fairway Players
Hancock, Anne Mette - Ruthless tr. Tara Chace #3 Journalist Heloise Kaldan and Police Officer Erik Schäfer
Hannah, Sophie - Hercule Poirot's Silent Night: The New Hercule Poirot Mystery #5 Hercule Poirot and Inspector Edward Catchpool of Scotland Yard
Harris, Jon - Murder in a Somerset Village #2 Julia Ford
Hattersley, Matthew - When The Kingdom Comes #2 John Beckett
Hill, Karl - The Surgeon
Hill, Reginald - A Candle for Christmas & Other Stories #Short Stories
Hodges, David - Storm on the Levels #12 DC Kate Hamblin
Hollow Mike - The Covent Garden Murder #8 Blitz Detective
Horst, Jorn Lier & Enger, Thomas - Stigma tr. Megan E Turney #4 Alexander Blix
Irving, Alison - Casual Cruelties
James, Alison - The House Guest
Kane, S W - The Drowning Place #2 DI Lew Kirby
Kelly, Julia - A Traitor in Whitehall #1 Evelyne Redfern, 1940
Koning, Christina - Murder in Cambridge (also pub. as End of Term under A. C. Koning) #5 The Blind Detective, 1920s
Leather, Stephen - Baltic Black Ops #5 Spider Shepherd: SAS
Mackay, Niki - The Due Date
Marston, Edward - Danger of Defeat #10 Inspector Harvey Marmion and Sergeant Joe Keedy
Martin, Laura - A Poisoned Fortune #3 Jane Austen Investigations
McCleave, Simon - The Colwyn Bay Killings #17 DI Ruth Hunter
McClure, Rob - The Scotsman
McDermid, Val - Past Lying #7 Karen Pirie
McKenna, Clara - Murder on Mistletoe Lane #5 Stella and Lyndy, 1905
McLean, Rachel (with Millie Ravensworth) - Death at Westminster #1 Diana Bakewell
Merritt, Chris - Committed #1 Ellen McGinley
Moloney, Catherine - Crime in the Allotment #20 DI Gilbert Markham
Morgan, Anna-Marie - The Park Murders #21 DI Yvonne Giles
Morris, M S - Days Like Shadows Pass #5 DCI Tom Raven
Morrison, Lynn - Double Cross Dead #4 Dora and Rex, 1920s
Morton, Mandy - Cat Among the Pumpkins #12 The No. 2 Feline Detective Agency
Moss, NJ - The Twins
Muir, T F - The Killing Mood #12 DI Andy Gilchrist & team, St. Andrews
Nixon, Keith - The Dead Can't Lie #8 Solomon Gray
O'Connor, Carlene - Some of Us Are Looking #2 Dimpna Wilde
Pearce, Biba - The Marlow Murders #7 Rob Miller, Police, London
Pearson, David - The Ferry Port Mystery #1 Wexford Homicides
Perry, Anne - A Christmas Vanishing
Perry, Karen - The Worst Thing You Ever Did
Phifer, Helen - The Haunting on West 10th Street #1 Detective Maria Miller
Pine, Alex - The Night Before Christmas #4 DI James Walker, Cumbria
Probyn, Jack - Death's Touch #3 DS Tomek Bowen
Puleston, Stephen - Stone Cold Dead #11 Inspector Drake
Rhodes, Kate - Hangman Island #7 DI Ben Kitto
Rigby, Sally (with Amanda Ashby) - The Stepmother
Riley, Vanessa - Murder in Drury Lane #2 Lady Worthing, Regency
Rose, M L - Hold Your Breath #5 DCI Rohan Roy
Sigurdardottir, Lilja - White as Snow tr. Quentin Bates #3 Arora
Sigurdardottir, Yrsa - The Prey tr. Victoria Cribb
Slater, K L - Husband and Wife
Smith, G N - The Shelter #3 Fiona MacLeish
Starr, Melvin R - A Polluted Font #16 Hugh de Singleton, Surgeon, 14thC England
Tuomainen, Antti - The Beaver Theory tr. David Hackston #3 Rabbit Factor Trilogy
Waller, Anita - Fatal Lies #2 Forrester Family
Watson, Sue - The Lodge
Wilkinson, Kerry - The Night of the Sleepover #1 Sleepover
Wood, Michael - Below Ground #11 DCI Matilda Darke
Yokoyama, Hideo - The North Light tr. Louise Heal Kawai