Charge by post-office on an Amazon order

I ordered a dictionary through amazon.com (from one of the US-based sellers listed in the website).  The dictionary plus shipping came to be around 40 Euros.  Today, I received a note from the Belgian post office stating that I need to pay 10 Euros to receive the item (Aanbiedingskosten aan het Douaneagentschap / Frais de Presetnation a l'Agence de 10,00 EUR).  Is this normal?