City of Masks is about a teenaged girl named Arianna who lives in 16th century Talia, who wants nothing more than to be a mandolier, and a boy named Lucian, who lives in 21st century England, and has an incurable case of cancer.
As Lucian suffers, his dad gives him a beautiful notebook from what seems to be very early Italy. When he fell asleep one night holding the notebook in his hand, he finds himself in 16th century Italy (Talia).
There he meets Arianna, and learns that how he got there was by what the experts call stravagation (which is how he was transferred from his world to this new one). So quite suddenly he is thrown into living two lives, one as a sick kid in modern England during the day, and the other as a perfectly healthy young man in Talia.
I recommend this exciting, kind of mysterious book for people who like fantasy and books that you don't want to put down.
City of Stars is an amazing book, the first in a series of 3. It is so wonderful for many reasons, one of which is that this book surprises you, (in a good way). While you're reading it's hard to guess what is going to happen, until it does, or nearly until it does.