TITLE: Intermediate Text in Combinatorics?
QUESTION [8 upvotes]: I'm currently attending a somewhat disorganized seminar on combinatorics that follows no textbook. So far we have covered the orbit-stabilizer theorem, some recursion, and we're heading into the Möbius inversion formula. 
Can anyone suggest a text that approaches combinatorics at this level for a 2nd-3rd year undergrad who already knows some algebra and the more basic combinatorics like combinations, permutations, stars-and-bars, generating functions? Most introductory combinatorics books I've found are more suited to a discrete math class and cover stuff which I already know. I'm looking for something to supplement this lecture. Thank you.

REPLY [7 votes]: I did a reading course in Combinatorics while a PhD student, and we used van Lint and Wilson which I thought was very hard, but very good.  You don't need any more background than you already have, and you will learn a ton from this text.
It's definitely not as well-known as the other suggested texts, but it many ways it's superior.  (Although Concrete Mathematics is a better book overall for its sheer beauty.)