You get what you pay for! This was a kindle freebie, and worth every penny I paid for it.
The premise required WAY too much suspension of disbelief - we're supposed to believe that a shy, sheltered 17 year old high school girl would buy a backpack and head off to the airport without knowing where she was going, to follow the trail of "little blue envelopes" - and we're supposed to believe that her parents would be okay with this and that the aunt who supposedly loved her would require this of her. We're also supposed to believe that the aunt would put her in potentially dangerous situations (such as instructing her to go out and pick up a strange boy in Rome).
The "plot" is pointless and the characters are shallow. Some of the characters she meets seem to have no purpose for being there at all. Others are to fill a role - the love interest, the wacky American family, the group of travelling students. But none of them are particularly interesting or memorable or well developed. The only question I had reading this was whether the aunt's intention was to get the girl laid (or possibly raped).
The whole idea might have made some sense with an older protagonist - you know, the 30-something, never really lived, never done anything, adult forced out of her shell to find adventures and love in the big world. Not with a high school kid, though.
Two good things about the book - it was free and it was a very quick read. That's pretty much it.