Murder in Black Letter Poul — Poul Anderson

A pre-Renaissance manuscript, an old treatise on witchcraft, and black magic feature in the murder of a quiet, young teacher at the University of California.
"The writer, already well know to science fiction readers, gives us a startling detective in his Norwegian-Japanese Trygve Yamamura who, this time, finds the murderer of a young university who knew too much about a medieval Book of Witches and who was tortured before his death. Good suspense and excellent puzzle." -- The Cincinnatti Enquirer