Here's a snapshot of what I think is published for the first time in August 2021 (and is usually a UK date but occasionally will be a US or Australian date). August and future months (and years) can be found on the Future Releases page. If I've missed anything or got the date wrong, do please leave a comment.
• Anthology: Many Deadly Return (ed. Martin Edwards)
• Allen, Jo - Death in the Woods (ebook only) #6 DCI Jude Satterthwaite, Lake District
• Amsinck, Heidi - My Name is Jensen
• Anderson, Lin - The Killing Tide #17 Rhona MacLeod, forensic scientist, Glasgow
• Batchelor, Penny - Her New Best Friend
• Bonda, Katarzyna - Conspiracy of Blood #2 Sasza Zaluska
• Calkins, Susanna - The Cry of the Hangman #6 Lucy Campion, Chambermaid, 17thC
• Cameron, Stella - The Playing Fields #7 Alex Duggins, Folly-on-Weir, Cotswolds
• Candlish, Louise - The Heights
• Carpenter, Elisabeth - The Vacancy
• Cavanagh, Steve - The Devil's Advocate #6 Eddie Flynn, USA
• Chaudhuri, A A - She's Mine
• Clark, Cassandra - The Day of the Serpent #2 Brother Chandler, 1399
• Conway, Simon - The Saboteur #2 Jude Lyon, MI6
• Croft, Elle - Buried
• Cutler, Judith - Death's Long Shadow #3 Matthew Rowsley, Steward & Mrs Faulkner, Housekeeper, Victorian Era
• Cutts, Lisa - Murder in the Village (ebook only) #4 Harry Powell
• De Giovanni, Maurizio - Bread For the Bastards of Pizzofalcone #5 Bastards of Pizzofalcone
• de la Motte, Anders - End of Summer #3 Seasons Quartet
• Dennison, Hannah - Danger at the Cove #2 Island Sisters
• Dixon, Patricia - The Other Woman
• Dunn, Matthew - The Spy Thief #5 Ben Sign, MI6
• Ellis, Kate - The Stone Chamber #25 Wesley Peterson (policeman) and Neil Watson (archaeologist), Tradmouth, Devon
• Ellwood, Nuala - The Perfect Life
• Feeney, Alice - Rock Paper Scissors
• Fitzek, Sebastian - The Soul Breaker
• Gatland, Jack - A Ritual For the Dying #6 DI Declan Walsh
• Grace, Ed - A Deadly Weapon #4 Jay Sullivan
• Gregory, Susanna - The Chancellor's Secret #25 Matthew Bartholomew, 14th Century physician, Cambridge
• Hamilton, Karen - The Ex-Husband
• Haughton, Emma - The Dark
• Hawkins, Paula - A Slow Fire Burning
• Hawkswood, Sarah - Wolf at the Door #9 Bradecote and Catchpoll, Worcestershire, C12 Bradecote and Catchpoll, Worcestershire, C12
• Holliday, Susi - Substitute
• Horowitz, Anthony - A Line to Kill #3 Detective Daniel Hawthorne
• Howard, Catherine Ryan - 56 Days
• Hrib, Bogdan - Resilience
• Huber, Anna Lee - Murder Most Fair #5 Verity Kent, England, 1919
• Hunter, M A - Repressed #5 The Missing Children Case Files
• Jameson, Emma - A Death at Candlewick Castle #2 Jemima Jago, Librarian, Isles of Scilly
• Jecks, Michael - The Moorland Murderers #6 Jack Blackjack, Tudor Era
• Jolly, Meg - The Mistakes We Deny #3 DI Ward, Yorkshire
• Jones, Sandie - The Guilt Trip
• Kent, Anna - The House of Whispers
• Kirk, JD - Colder than the Grave #8 DCI Logan
• La Plante, Lynda - Unholy Murder #7 WPC Tennison
• Lawrance, Jodie - The Evidence #2 Detective Helen Carter, Edinburgh, 1970s
• Legat, Anna - Death Comes to Bishops Well #1 Shires Mysteries
• Louth, Nick - The Body on the Moor #8 DCI Craig Gillard
• Mark, David - Darkness Falls #1 McAvoy Prequel
• Marsh, JJ - Wolf Tones
• Marshall, Laura - The Anniversary
• McDermid, Val - 1979 #1 Allie Burns, Journalist
• McDermott, Alan - When Death Strikes #4 Eva Driscoll
• McGeorge, Chris - Half-Past Tomorrow
• McIver, Ruth - I Shot the Devil
• McLean, Rachel - The Island Murders #3 DCI Lesley Clarke, Dorset
• Mo, Johanna - The Night Singer #1 Detective Hanna Duncker
• Morris, Vera - The Great Shroud #5 Anglian Detective Agency series
• Paulson-Ellis, Mary - Emily Noble's Disgrace
• Robb, Candace - The Riverwoman's Dragon #13 Owen Archer
• Robson, Amanda - The Unwelcome Guest
• Rose, C E - The House on the Water's Edge (ebook only)
• Russell, Leigh - Deep Cover #16 DI Geraldine Steel
• Saunders, Kate - The Mystery of the Sorrowful Maiden #3 Laetitia Rodd, Private Detective, Victorian Era
• Sennen, Mark - Puppet (ebook only) #7 DI Charlotte Savage
• Sharp, Zoe - Trial Under Fire #1 Charlie Fox Prequel
• Sheridan, Sara - Celtic Cross #9 Mirabelle Bevan (retired Secret Service), 1950s
• Silver, Abi - The Midas Game #5 Burton and Lamb
• Sivakumaran, Anita - Cold Sun
• Skelton, Douglas - A Rattle of Bones #3 Rebecca Connolly
• Smith, Alex - Every Mother's Son #6 DCI Robert Kett, Norfolk
• Spencer, Sally - Poison #14 DCI Monika Paniatowski, Whitebridge
• Sykes, S D - The Good Death #5 Oswald de Lacy, 14C Kent
• Temple, Rose - A Fatal Move (ebook only) #3 ex-Met PC Jemima Cotton, Little Cote
• Trinchieri, Camilla - The Bitter Taste of Murder #2 Nico Doyle, Chianti, Italy
• Unge, Christian - Hell and High Water #1 Dr Tekla Berg
• Waller, Anita - Blood Red
• Young, Glenda - Murder at the Seaview Hotel #1 Helen Dexter, Scarborough