Zafon always hints honestly at his sources, and references to Les Miserables acknowledge that this is, partially, a "hommage" to Victor Hugo. There is also another nod to Great Expectations, and some riverside scenes put me in mind of Vincent Price's camp extravaganza The Theatre of Blood!
The first 50 pages of this keenly awaited new novel suffer from an uneven pace and, for a book set in the 1930s and 50s, there are some jarringly modern words (Zafon's fault or the translator's?). An intermittently humorous tone, together with the plot emphasis on Fermin's impending wedding and David Martin's not-so-secret passion for Daniel Sempere's mother Isabella, nudge the book to the edge of romantic comedy. It's only the prison scenes that are rich in atmosphere and pop a surprise or two.
What we expect from Senor Zafon (and Isabel Allende and Salman Rushdie) is Magic Realism. This time Zafon serves up a bit more realism and a lot less magic. From almost any other author The Prisoner of Heaven would be regarded as a considerable achievement but The Shadow of the Wind was a magnificent achievement, raising the bar for all authors, including Zafon. In The Prisoner of Heaven he seems to be "treading water". It's a good book, but it's not a great book.