There are 3 books in the Lord John Grey series. The newest book is The Scottish Prisoner which came out in 2009.

1
Lord John and the Private Matter

Book cover of Lord John and the Private Matter
NEW YORK TIMES BESTSELLER • Diana Gabaldon weaves a dazzling tale of history, intrigue, and suspense in this first novel featuring one of her most popular characters from the Outlander saga: Lord John Grey.
 
The year is 1757. On a clear morning in mid-June, Lord John Grey emerges from London’s…
When you buy books, we may earn a commission that helps keep our lights on (or join the rebellion as a member).

2
Lord John and the Brotherhood of the Blade

Book cover of Lord John and the Brotherhood of the Blade

NEW YORK TIMES BESTSELLER
 
Diana Gabaldon, the #1 New York Times bestselling author of the Outlander saga, brings back one of her most compelling characters: Lord John Grey. Here Gabaldon weaves together the strands of Lord John’s secret and public lives—a shattering family mystery, a love affair with potentially disastrous…

3
The Scottish Prisoner

Book cover of The Scottish Prisoner

From the international bestselling author of the Outlander series, the terrific new novel featuring the ever-popular Lord John.

1760. Jamie Fraser is a paroled prisoner-of-war in the remote Lake District. Close enough to the son he cannot claim as his own, his quiet existence is interrupted first by dreams of…