I'm usually I huge fan of Carlos Ruiz Zafón. The Shadow of the Wind is one of my absolutely favourite books and I love to loose myself in the labyrinth of the Cemetery of Forgotten books.
Las Luces de Septiembre is one of his early works written for young adults. I enjoyed the very creepy atmosphere Mr Zafón creates. There is also an appearance of Andreas Corelli (known from The Angel's Game) which I definitely liked. But the whole story just seemed very constructed and left unexplained a few things. Clearly not his best work.