I suppose it isn't entirely paradoxical, but I disliked the dragon book, even though I rather liked Hopcroft/Motwani/Ullman's (theoretical, non-compiler book) Automata Theory, Languages, and Computation. (Turing award winner) Ullman giveth and taketh away.

Purple dragon (Aho/Lam/Sethi/Ullman) is probably better than red (or green) dragon though, as it adds some interesting topics.

In an undergrad course, I'd probably prefer a simple book that uses recursive descent.