Book 45 The Magus of Hay by Phil Rickman
This is the twelfth book in Rickman's series featuring Merrily Watkins, vicar ofa small parish in the Herefordshire countryside and diocesan exorcist for Hereford. She is called in by a police officer she has worked with many times before to have a look at the home in a tiny hamlet near Hay-on-Wye of a man in his 90s found dead in a nearby tributary of the Wye. The house includes a library of the occult and esoteric, and evidence that the man was a practitioner of chaos magic. Although the death itself is not suspicious, a local young policewoman takes it on herself to investigate the man's background and just what went on at this remote home, as does Merrily. At the same time, a pagan couple Merrily has encountered before are setting up a bookshop in Hay itself, and discovering that the shop they are renting has a bit of a sinister past. Then the policewoman disappears.
Rickman is a very prolific author - 12 in this series, two books so far featuring Dr John Dee, and a series of stand alone novels whose characters sometimes make an appearance in the world of Rev Watkins. I really enjoy his novels and last year, having picked up the first in the Watkins series in a bookshop in Hay, actually read the 11 that had then been published in just over a month. He always has this pagan/occult interest in his novels as far as I can see and handles it very deftly with an awful lot of knowledge and clear research.