Eli Bendersky's website It happens often that after some book by an author becomes very popular, his earlier books suddenly appear in the limelights as well (Dan Brown would be one good example). "Marina" is one such book. It was written a few years before Zafón's most popular work - "The Shadow of the Wind". And now it heralds the subtitle "the unforgettable history that preceded The Shadow of the Wind", although it's a completely different story. OK, so the Spanish publishers use all the same dirty tricks as American ones :-)
As commonly happens with such books (again, Dan Brown is an example) - they are quite similar. Indeed, "Marina" is in many senses similar to "The Shadow of the Wind". It has a teenage protagonist that narrates the novel, a touching love story, a mystery that gets uncovered step by step, and it's also somewhat dedicated to the city of Barcelona. It's a much shorter book (only 290 pages in a rather small format), but has most of the basic elements. It's almost as if this was Zafón practicing for his real novel.
But enough comparisons. By itself, "Marina" is a pretty good book as well. Nicely written, interesting and unusual. It delves into science fiction a little, which I didn't like, but other than that it was quite enjoyable.