When travelling, I like to read about where I am, so historical fiction is often a companion. In terms of atmosphere and evocation of a place, fiction has it hands down over guide books. The next three books mentioned accompanied me to Europe recently, and were excellent travel companions although very different from each other.
The Lady & the Unicorn is a fanciful riff on the history of the fabulous tapestries in Paris at Cluny, or the Musee du Moyen Age. While very little is known about their designer or weaver, Chevalier takes what is known about the times and the family that commissioned the tapestries and fills in the blanks in an entertaining and informative read. If you've had the good fortune to see these tapestries, you'll enjoy this novel.