Daniel, overwhelmed by rage and need to avenge the death of his mother, Isabella, will discover a network of crimes and violations of Francoist Spain, and a new protagonist, Alicia Gris, will help him solve the mysteries.

The novel is arranged into alternate chronologies labeled after liturgical prayers and the Catholic requiem mass: Dies Irae, Kyrie, Agnus Dei, Libera Me, and In Paradisum.

[14] On the November/December 2015 issue of Bookmarks, the book received a (4.0 out of 5) with the critical summary saying, "Zafón brings the reader full circle in this magical novel, completing the story he began with The Shadow of the Wind and creating “a satisfying conclusion to a grand epic” (Kirkus)".

Publishers Weekly called it a" gripping and moving thriller," adding that "fans of complex and literate mysteries featuring detectives with integrity working under oppressive and corrupt regimes will be well satisfied."

The Irish Times opined that "this is a novel to lose oneself in, and it promotes the sort of reading experience we remember from childhood – of complete absorption into a fantasy world – but rarely attain in later life.