Novels of Espionage: Boxed Set

This boxed set includes 8 classical spy novels, set at the beginning of the 20th century:
THE CZAR'S SPY BY WILLIAM LE QUEUX
THE INTERNATIONAL SPY (BEING THE SECRET HISTORY OF THE RUSSO-JAPANESE WAR) BY ALLEN UPWARD
THE RIDDLE OF THE SANDS BY ERSKINE CHILDERS
THE POWERS AND MAXINE BY C.N. AND A.M. WILLIAMSON
ELUSIVE ISABEL BY JACQUES FUTRELLE
I SPY BY NATALIE SUMNER LINCOLN
JENNIE BAXTER JOURNALIST BY ROBERT BARR
THE IVORY SNUFF BOX BY ARNOLD FREDERICKS