The Lodger. by Marie Belloc Lowndes

The Lodger is the first known novelization of the Jack the Ripper story. It follows the lives of Mr. and Mrs. Bunting, a maid and butler. An eccentric lodger, Mr. Sleuth, arrives at their lodging-house just as a wave of horrific murders begins to sweep London. The Buntings become engrossed in the newspaper sensationalism as well the detailed accounts of their young friend, a Scotland Yard detective.
Lowndes first wrote The Lodger as a short story published in McClure's Magazine, then later published the novelization in the Daily Telegraph as a serial. It was very successful, with over a million copies sold within a few decades. Writers like Ernest Hemingway and Gertrude Stein praised it, with one contemporary reviewer calling it "the best novel about murder written by any living author". It has since been adapted to other media, notably as one of Alfred Hitchcock's first movies.
Today the novel is still considered the best fictional adaptation of the Jack the Ripper legend.