Smyth's debut adult fantasy murder mystery is The Undetectables.
At Tor.com they tagged five books featuring an unlikely alliance with a ghost, including:
Under the Whispering Door by TJ KluneRead about another entry on the list.
Wallace Price cannot be dead. He certainly cannot be dead wearing casual Sunday-in-the-legal-office clothes. He most certainly cannot be dead, because if he was dead, more people would be at his funeral. He’s brought to a highly unusual tea shop run by Hugo, a reaper who wants to help Wallace cross over, even if Wallace is not ready to go. Told from the POV of the ghost in question, the unlikely alliance between ghost and the human(-of-sorts) is an utterly heart-crushing romance, as well as a deep delve into the depths of what makes us human when we’re no longer living. It emotionally destroyed me, and that’s why I’d recommend it wholeheartedly. After all, who doesn’t love a book that has the redemptive essence of A Christmas Carol in a very, very queer, fantastical setting?
--Marshal Zeringue