For decades, the humble crossword was the commuter's companion, a paper puzzle to fill the gaps of a metro ride or a waiting room. Today, that role has been usurped by a new breed of publication: the adult activity book. In Spain, this genre has exploded, with titles that combine sudoku, pop culture trivia, and even murder mysteries. Leading the charge is Murdoku, a purple-covered notebook that has sold more than 140,000 copies and turned puzzle-solving into a cultural event.
From colouring books to crime-solving
The current craze has its roots in the adult colouring book trend of a decade ago, marketed as art therapy or anti-stress. That fad proved more than a summer flash in the pan, evolving into a more ambitious format: the activity book that updates the classic newsstand puzzle collection with a hefty dose of popular culture. References to Rosalía, Netflix series, and football stars now sit alongside crosswords and word searches, making the books feel contemporary and engaging.
This evolution has not been stifled by the smartphone era. Instead, analogue and digital pastimes coexist, much like cookery shows on YouTube have not killed the recipe book. The success of these books suggests a growing appetite for activities that demand focus without the constant ping of notifications.
Blackie Books and the Cuaderno phenomenon
Barcelona-based publisher Blackie Books was an early mover. Its adult activity books, now in their 14th volume, have sold over 250,000 copies. The latest edition offers 60 exercises spanning music, film, literature, and science, designed to “de-rust the mind.” The publisher has expanded the concept with a children's version, a “Golden” edition for older readers, and a Catalan-language version that features local icons like Mercè Rodoreda and the castellers.
Other publishers have carved out niches. Debate released an activity book by satirical site El Mundo Today that tests readers' ability to distinguish reality from fiction, while GeoPlaneta's travel-themed activity book, now in its fifth volume, includes playlists and gastronomic guides.
Murdoku: the sudoku-murder hybrid
The standout hit is Murdoku, created by Canadian puzzle designer Manuel Garand. Each puzzle presents a grid of suspects; by applying sudoku logic, readers deduce the victim's location and thus the killer. The difficulty ramps up as the book progresses, and some bookshops now host live solving competitions. The concept has even spawned a free online version, with 35 puzzles available at the time of writing.
Murdoku's success has inspired imitators. Murdle, by American G.T. Karber, uses narrative clues about suspects, weapons, and settings instead of a grid. It has already spawned three volumes and a children's edition. Espasa has published Los casos de Agatha Christie, an official activity book that lets readers step into the shoes of Poirot or Miss Marple. Other titles like El crimen del verano and Crimigramas embed mysteries within crosswords and word searches.
This fusion of puzzle and plot transforms the reader from passive consumer into active detective, a shift that seems to resonate deeply. The genre's appeal is not just about entertainment; it also speaks to a broader desire to disconnect from screens. Many of these books are explicitly marketed as a digital detox, offering a slower, more mindful form of leisure.
While there is no scientific study yet confirming the cognitive benefits, enthusiasts argue that these puzzles exercise attention, memory, and mental flexibility. Whether or not they can compete with the sophistication of video games is beside the point; the appeal lies in their simplicity and the satisfaction of solving a mystery with nothing more than a pencil and an eraser.
As the trend continues to grow, it is clear that the adult activity book has become more than a passing fad. It is a cultural phenomenon that reflects a collective yearning for analogue engagement in a digital world. For those looking to escape the constant buzz of modern life, these books offer a welcome reprieve—one puzzle at a time.
