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.”

7 to 12 

by Anna Katharine Green is a detective novel presented as one of her earlier tales.  It is a quick, fast-paced mystery sure to have the reader turning pages.

6 Seconds of Darkness by Octavius Roy Cohen

Energetic sleuth David Carroll, whose probe into police corruption has made him unpopular at headquarters, is put in charge of an investigation into the shooting murder of civic reformer Edward Hamilton -- and the three people trying to confess to the crime! It develops into an unusual and interesting plot.

 The Woman Aroused by Ed Lacy

Principal Characters
GEORGE JACKSON
Since splitting up with his wife, he had seen her occasionally but then he met Lee—and no other woman would do!
HENRY CONLEY
He came to George with $7,000. When he died George didn't know what to do with the money—or Henry's wife either!
LEE CONLEY
Tall, voluptuous. Next to her Lady Godiva looked like the winner of a baby contest. But no man could unlock the secret she kept from the world!
FRANCIS F. HENDERSON
George's retired neighbor. He played poker to win money and loved to look into his neighbor's windows. He gave his age as reason enough for both forms of indulgence.
JOE COLLINS
Worked for same company as George. A middle-aged Romeo, he got quite a shock when his son came home from overseas and acted just like him!
WALT COLLINS
Joe's son. His father had planned for him to go to college when he was discharged but the Army had taught Walt a lot, and he was changed now, changed into a wise guy—with angles!
FLO JACKSON
George's estranged wife. She saw him every now and then and they tried to start over, but when Lee came into the picture, her chances sank to a new low!

 Prince Zaleski by M. P. Shiel

If you find Holmes and Poirot insufficiently cerebral, a little too everyday action hero, then Zaleski is the detective for you. Exiled and lovelorn, he broods alone (but for a black manservant, of whom frankly the less said the better) in a wing of a ruined abbey set among cypresses and poplars. We first see him reclining beside a partially-unwrapped mummy, "discarding his gemmed chibouque and an old vellum reprint of Anacreon". From the opulent, narcotic haze of this sanctum he declines to shift for the first two adventures, unravelling otherwise insoluble mysteries of ancestral curses and ancient gems simply from what is reported to him by the narrator Shiel, who might thus be considered a far more poetically-inclined Watson. Shiel considered himself Doyle's superior, and the solutions are exactly the sort of thing someone might come up with when they're trying to outdo Holmes but haven't twigged the very precise - if indefinable - limits of fairness in a puzzle; everything hinges on word association, dubious scholarship and the like, such that the reader's reaction is less likely to be 'Good heavens!' that 'You what?' But in Holmes the intricate solutions were only ever part of the appeal, and in Zaleski they're barely even that. It's the atmosphere that matters. And in the last of these three original stories*, that atmosphere is whipped into such a ferment that you start to wonder if Shiel (the writer) was receiving some distorted yet overwhelming vision of the future. True, there is the line at which one can only respond with a hollow laugh, where Zaleski tells his friend that war will doubtless be extinct within their lifetimes. But otherwise...an epidemic of murder and insanity which begins in Germany. Eugenic tirades. Visions of a future society in which technological advancement goes hand-in-hand with sacrificial hecatombs devoted to preserving the purity of the race. And the story is entitled 'The S.S.'.

Fifty Years A Detective by Thomas Furlong
Thirty five true stories told by a man who was a detective for fifty years. A remarkable book.
This hardcover book is equipped with a colorful  dust jacket.  It is great for gifts, libraries, and home libraries.
There is a paperback available HERE and an epub available HERE.