This book also appears under the title, "In My Enemy's Arms," which is rather more scandalous sounding and not very accurate.

A very exciting chase through Europe at the conclusion of the first world war. Harry, a British soldier, has ended up in a German occupied hospital and is about to be sent to a prisoner of war camp, but then he's offered a chance for freedom. All he has to do is agree to escort Princess Irena out of her home country and over to England. She'll be running for her life from crafty and ruthless political foes. He agrees to this. The only catch is that he'll have to marry her, so as to make her entrance to England permissible. Then they will get an annulment after her safety is assured. Or such is the plan.
They have a number of close escapes and sticky situations. The book is mostly in the action/adventure genre and is a pretty quick read. It is also funny at times, and of course there are Complicating Feelings. ( )