How can a character from a children’s book become so divisive that he causes arguments amongst adults? This essay uses transactional reader response theory to explain the reason why the character Severus Snape from the Harry Potter book series by J.K. Rowling is so controversial. Applying notions from reader response theorists such as Rosenblatt and Iser together with earlier research on Snape will show how the reader’s opinion is affected by both the text itself and their own personal experience. A poll was created and posted on Facebook with over a thousand replies. This data is analysed and used to apply the theory on real examples. The conclusion of the essay is that Snape is both good and bad. He acts heroically but is also vindictive and petty. Snape is perhaps the most human of all Rowling’s characters and each reader recognises a little of themselves in him that they can relate to. Because of ongoing arguments regarding Snape readers have to constantly defend their opinion. As the opinion is re-evaluated it is also strengthened each time readers reconsider the story of Snape and, like Snape himself once asked Professor Quirrell to do, decide where their loyalties lie.