A seasoned tempter advises a novice devil on the art of corrupting a young Catholic, while navigating his own infernal politics and temptations. Master Tempter Slubgrip corresponds daily with the less experienced Dogwart, offering guidance on how to tempt a confused young Catholic. Simultaneously, Slubgrip must manage his own assigned 'patient'—an older Catholic man facing a severe illness—and contend with rival under-devils plotting to usurp his infernal territory. The narrative unfolds through these epistolary exchanges, charting a course from Shrove Tuesday through to Easter Day.

The provided description frames 'The Gargoyle Code' as a work of satirical religious fiction, drawing comparisons to C.S. Lewis's 'Screwtape Letters'. The narrative structure, presented as a series of diabolical correspondences, suggests a focus on theological themes explored through humor and a unique infernal perspective. The book's design to be read during Lent indicates an intention to engage readers with spiritual concepts in an accessible and entertaining manner, charting a course through the Easter season. The reception, as suggested by the description, is likely to appeal to readers who appreciate witty, thought-provoking explorations of faith and temptation.