What was the purpose of the introduction in the Murders in the Rue Morgue?

Well I think he was building up the concept of ratiocination before introducing the character that is a living embodiment of it. But he's also encouraging the reader to think outside the box, which makes sense given who the killer turns out to be. This was apparently the first detective story, so it may have been fresher and more interesting when it was written than it reads now.