The presentation was great; no worries there.
The story left me a little cold; it was well-handled, but it felt a little too much like formulaic urban fantasy for me to really enjoy it, from the unwilling hero to the dime-novel detective trappings to the MacGuffin with unspecified ultimate power in it. Even the demon wasn't particularly striking or interesting - cold aura, cloven hooves, dark cloud, yadda yadda - and the climactic fight scene wasn't very. (And honestly, if the purple eye can be exploded by a simple paradox, it's amazing it survived as long as it did.) The discussion of logic was the most interesting part of the story, but I was disappointed that it turned out to just be laying the groundwork for the "No man of woman born can slay Macbeth" ending to the demon battle. I'd have been interested in a story that explored the idea of paradoxes a little more thoroughly, in the way that "The Axiom of Choice" explored free will and consequences.