The art of Juan Ruiz must be understood in the light of the medieval conception of art as facere, a conception that postulates the artistic independence of a work while emphasizing its didactic nature in the use that individuals can make of it following their own personal motivations. The independent artistic form of Ruiz's work is at the same time an autobiographical form, wherein lies its fictional character. The fiction of the Book of Good Love is not to be seen as the fiction of its imaginary adventures but as the psychological fiction of its protagonist, i.e., the literary illusion that this protagonist mistakes for reality. Such an illusion is best exhibited in the central episode of the book, that of don Melón and doña Endrina, Ruiz's own amplified translation of Pamphilus de Amore. The autobiographical form of the book, therefore, should not be seen as a conventional literary device for self-expression but as an ironic portrait of Juan Ruiz, the man, taking for reality what Juan Ruiz, the artist, knows to be only literary fiction. (In Spanish)