Too Many Magicians
by Randall Garrett
The novel takes place in 1966. However, it occurs in a world with an alternative history. The Plantagenet kings survived and rule a large Anglo-French Empire. In addition, around AD 1300 the laws of magic were discovered and magical science developed. The physical sciences were never pursued. The society looks early Victorian, though medical magic is superior to our medicine.
The book uses the conventions of a detective story. The protagonist is Lord Darcy, Chief Investigator for the Duke of Normandy. This Sherlock Holmes-like figure is assisted by Master Sean O'Lochlainn, a forensic sorcerer.
The novel is a locked room mystery, which takes place at a wizards' convention. Garrett delights in puns. Analogues of Nero Wolfe, Archie Goodwin, James Bond and Gandalf the Grey appear.
Lord Darcy also appears in several other novellas and short stories by Garrett, but this is Garrett's only novel-length Lord Darcy story. Michael Kurland has written two further novels set in the Lord Darcy universe.