The Twelfth Department

William Ryan's first novel in the Captain Korolev series, The Holy Thief, was shortlisted for a Crime Writer's Association's New Blood Dagger, a Barry Award, The Kerry Group Irish Fiction Award and The Theakstons Old Peculier Crime Novel of the Year. The second in the series, The Bloody Meadow, was shortlisted for the Ireland AM Crime Novel of the Year and the third, The Twelfth Department, was also shortlisted for the Ireland AM Crime Novel of the Year as well as the CWA's Historical Fiction Dagger and was a Guardian Crime Novel of the Year..

The Constant Soldier, William's fourth novel was described as "subtle, suspenseful and superb" by The Daily Mail and shortlisted for the HWA's Gold Crown and the CWA's Steel Dagger. A House of Ghosts, (as W.C. Ryan),was published in October 2018 and was described as "an intelligent, absorbing, exquisitely spooky mystery" by The Irish Times. The Winter Guest, published in January 2022, was called an "impeccably researched and utterly intriguing historical mystery that lays bare the societal fractures caused in Ireland’s fight for freedom" by the Irish Independent.