Luckily, we are assured that the books can be read in any order. Only belatedly did I realise that this is actually the third novel in Zafón's sequence. But beneath the sugared surface there is also political anger. Much of the novel's appeal is that of time-travelling tourism, strongly flavoured with literary nostalgia – for a time when a bookshop could be a city's cultural nerve-centre, when a paper-based bureaucracy could be outwitted, when bohemian scribblers could afford to eat world-class crème caramels, and even when money could be 'cursed'. (The novel's epigraph is by a fictional writer who featured in The Shadow of the Wind.) This is explicitly, and joyously, a book about books, about what can be learned from them (say, how to follow someone in the street), and what is lost when they are lost. Like his countryman Arturo Pérez-Reverte, Zafón combines sincere engagement with genre tradition, with clever touches of the literary postmodern.

When Daniel complains that it is impossible to argue with him, Fermín shoots back: 'That's because of my natural flair for high dialectics, always ready to strike back at the slightest hint of inanity, dear friend.' By the end, it's clear that Fermín is not just a comic turn but a kind of hero of resilience.

The most vividly lovable person here is Fermín, a master of comically flowery rhetoric, who claims that 'obstetrics, after free verse, is one of my hobbies'. The evil prison governor, whose eyes are 'blue, penetrating and sharp, alive with greed and suspicion', is a movie-villain cliché, but cliché is sometimes just what is needed to maintain the blissful narrative drive of a high-class mystery. Scene-setting is crisp, and minor characters expertly sketched: a priest with 'the manners of a retired boxer', or a scrivener who guarantees the effects of his erotic love poetry.

Melodrama succeeds when there is no embarrassment in its execution, and Zafón is a splendidly solicitous craftsman, careful to give the reader at least as much pleasure as he is evidently having. Set in a prison castle after the victory of Franco in the civil war, with an ambience of lice, cold and summary executions, it features a novelist, imprisoned and denounced as 'the worst writer in the world', who is blackmailed into polishing the prison governor's own execrable literary efforts.

As with The Shadow of the Wind, there is a historical story within the story.

The prisoner of heaven book