On www.bookfinder.com, you can order any book you want from any bookstore in the world that has it in stock.
Enter an author name, a keyword from the title, or both. Choose the language of the book you're looking for -- English, French, Italian, Dutch, German, or Spanish. Then pick a shipping destination and a currency. Click "Search".
Voilà! You get a list of all the books that match your search. Click on a title and you'll see all the online bookstores that carry that book, either new or used. The price noted includes shipping to the destination you chose.
The cheapest new copy of Valérian, tome 2, L'Empire des mille planètes, costs US$19.56 (shipping to the US included) from a French-language bookstore listed on Amazon.ca.
This is an incredibly useful website to order any kind of book you want from wherever you live. Have fun!