Sentence:  But with non-slash & non-porno, the best <WSD>Snapefic</WSD> I've read is "A Father's Sin" by Severitus, … in which the professor discovers an unlikely student at Hogwarts is his son. 
Meaning of the word marked with <WSD> tags:  A fanfic in which Severus Snape, of the "Harry Potter" series, is the protagonist.