The book is a systematic treatment of the ascetical life in pursuit of mystical union with Christ, giving advice and reporting on his own experience.
Written between 1578 and 1579 in Granada, Spain, after his escape from prison, the Ascent is illustrated by a diagram of the process outlined in the text of the Soul's progress to the summit of the metaphorical Mount Carmel where God is encountered.
The work is divided into three sections and is set out as a commentary on four poetic stanzas by John on the subject of the Dark Night.
John shows how the Soul sets out to leave all worldly ties and appetites behind to achieve "nothing less than transformation in God".
Aquesta me guiaba más cierto que la luz de mediodía adonde me esperaba quien yo bien me sabía en parte donde nadie parecía.
En mi pecho florido, que entero para él solo se guardaba allí quedó dormido y yo le regalaba y el ventalle de cedros aire daba.
El aire de la almena cuando yo sus cabellos esparcía con su mano serena en mi cuello hería y todos mis sentidos suspendía.
[1] John's poem contains these famous lines of self-abnegation leading to spiritual rebirth:[2] To reach satisfaction in all desire its possession in nothing.