The House of Mystery by William Henry Irwin

The House of Mystery by William Henry Irwin

Great premise: Guy looses gal to aunt who is training her to be medium. He fights back with his own 'seer'.'

The Mouse in the Mountain by Norbert Davis

The Mouse in the Mountain by Norbert Davis

Doan is a detective and Carstairs his enormous canine companion (don't call him a "pet"), and in this first hard-boiled adventure they travel to Mexico, along with an heiress, a revolutionary, an artist, and more than a few mysteries.

Holocaut House by Norbert Davis

Holocaust House by Norbert Davis

Doan, the "hero" of this story is a small-time detective with a dry, sardonic wit, a huge Great Dane, and the ability to defend himself quite well if the situation demands it. In Holocaust House he is given the job of protecting a young heiress who is on the verge of inheriting millions.

The Treasure Train by Arthur B. Reeve

The Treasure Train by Arthur B. Reeve

A railroad Vice President and and his chauffeur have sudden and mysterious seizures on the way to work; a family in New York city undergoes an epidemic of beri-beri; the American consul in the Virgin Islands collapses and dies for no apparent reason; a Wall Street speculator is apparently stabbed to death--with a rubber dagger. Who other than Craig Kennedy, armed with his knowledge of chemistry, technology and Freudian psychology could solve these mysteries?

The Photographer's Evidence by Nicholas Carter

Nick Carter stands for an interesting detective story. The fact that the books in this line are so uniformly good is entirely due to the work of a specialist. The man who wrote these stories produced no other type of fiction. His mind was concentrated upon the creation of new plots and situations in which his hero emerged triumphantly from all sorts of troubles and landed the criminal just where he should be—behind the bars.

A Battle for Right; Or, A Clash of Wits by Nicholas Carter

The blurb says:

Nick Carter stands for an interesting detective story. The fact that the books in this line are so uniformly good is entirely due to the work of a specialist. The man who wrote these stories produced no other type of fiction. His mind was concentrated upon the creation of new plots and situations in which his hero emerged triumphantly from all sorts of trouble, and landed the criminal just where he should be—behind the bars.

The author of these stories knew more about writing detective stories than any other single person.

The Cask by Freeman Wills Crofts

THIS book introduced to the public a new Master of Detective Fiction, and Mr. Crofts is now a very famous name indeed to the many enthusiastic students of detective novels. It has all the great virtues; a mysterious murder cunningly conceived and carried out; the strongest suspicion ingeniously thrown on an innocent man; a subtle alibi brilliantly shattered by an unfaltering process of analysis. The book is flawless in design and presents an intellectual problem of supreme interest. The lover of detective stories can want nothing better. As the Outlook said, “In construction and invention Mr. Crofts has no living equal.”