By: Joshua Glenn

Meneer [Mister] X (c. 1928), by Valentine Williams.

By: Joshua Glenn

Mr. X contra Scotland Yard (1949), by Martin Porlock.

By: Joshua Glenn

De Afschuwelijke X (c. 1946), by R. Poupon.

By: Joshua Glenn

Christopher Lee’s ‘X’ Certificate (1975)

By: Joshua Glenn

Organization X (1954), by Hermann Hilgendorff.

By: Joshua Glenn

Mr. X: King of the Underworld (1942), by Jack Lester.

By: Joshua Glenn

Laboratory X

By: Joshua Glenn

Nebula X

By: Joshua Glenn

The “X” People

By: Joshua Glenn

Assignment X

By: Joshua Glenn

Minus X

By: Joshua Glenn

Planet X

By: Joshua Glenn

21 great adventure novels of the Seventies!

By: Joshua Glenn

21 great adventure novels of the Sixties!

By: Joshua Glenn

21 great adventure novels of the Fifties!