The only novel written by Quevedo, it is presented in the first person singular and chronicles the adventures of Don Pablos, a buscón or swindler. Pablos sets out in life with two aims: to learn virtue and to become a caballero (gentleman). He fails miserably in both.
El Buscón has been considered a profound satire on Spanish life, but also as a literary exercise for Quevedo, in that he was able to utilize word-play and verbal flourishes and his skill as a literary caricaturist. El Buscón also propounds the notion that children of parents without honor will never be able to achieve honor themselves.
C. Brian Morris has written that Quevedo pursues Pablos with a series of "desgracias...encadenadas" ("linked calamities"). James Iffland describes these "linked calamities" as a "torturously up and down, bouncing trajectory which marks Pablos's career from the outset."
Quevedo satirizes Spanish society, but also attacks Pablos himself, who attempts throughout the novel to achieve a higher station in life and become a gentleman. Such aspirations from the lower classes would only destabilize the social order, in Quevedo's eyes. Quevedo punishes Pablos for attempting to better himself. "For Pablos, human society is the only reality. He knows no other. He is young, innocent, a little foolish." Eventually, Pablos is driven to become a pícaro, or rogue.
The work also incorporates autobiographical elements. In 1608, Quevedo dueled with the writer and fencing master Luis Pacheco de Narváez as a result of Quevedo criticizing one of his works. Quevedo took off Pacheco's hat in the first encounter. They were enemies all their lives. In El Buscón, this duel is parodied with a fencer relying on mathematical calculations having to run away from a duel with an experienced soldier.
Quevedo makes an early references to the effects of syphilis when he puns in his Buscón about a nose entre Roma y Francia meaning both "between Rome and France" and "between dull and eaten by the French illness".
Picaresque works are valuable linguistically because they record the argot of many sectors of society -both the language of the antihero and the criminals the antihero meets on his travels. Quevedo's novel gives a considerable amount of information about Germanía, or Thieves' cant.