13 Little Blue Envelopes

I started to read 13 Little Blue Envelopes by Maureen Johnson. The book is about a girl whose aunt disappears. She decides to go to the place where her aunt lived and found a package with her name on it. When she opened it she found 13 blue envelopes. Each envelope had instructions inside of it, but she couldn't open the next one until she was in the place where the previous one told her she needed to be. The envelopes take Ginny all over Europe to see some amazing sights and to see what her aunt saw.