Scottish Ghost Stories?

[MacMillan of Rathdown]

While each of the books is a stand alone novel, the first book does provide useful background on the characters of Adam Sinclair, Inspector McLeod, and Peregrine Lovat, so it might be worthwhile scouting out a used copy of the first book before diving into the series.

The book isn't technically out of print, just between printings, and at least two more Adapt novels are in the pipeline. One is set in the 1890s, and another is set in the immediate post-WWII period and bridges the story (and characters) found in Kurtz's LAMMAS NIGHT.