@saab,
It can even be detrimental in some views. The Dan Brown books have made some cities in Italy (Volterra is one, if I remember) infested with tourists who are not so much interested in history as the "story" in a novel. However, presently, people in Florence/Firenze are looking forward to the publishing of his new novel about Dante, as tourism has been down by 10% and the tourists that do go have been spending less.
On Wallander, I've liked the Mankell books I've read. A fair part of why I read police procedural books is to "visit" different countries; thus I've visited Sweden and Norway and the Netherlands, and France, Germany, England, Scotland, Ireland, Italy, Brazil, Mexico, Japan... and many other countries in my mind through the books. Of those, I've only been to Mexico and Italy in actual life.