Longinus 
On the Sublime [EPUB ebook] 

According to Wikipedia: 'Longinus is the conventional name of the author of the treatise On the Sublime, a work which focuses on the effect of good writing. Longinus, sometimes referred to as Pseudo-Longinus because his real name is unknown, was a Greek teacher of rhetoric or a literary critic who may have lived in the 1st or 3rd century AD. Longinus is known only for On the Sublime.’