How is Catcher in the Rye a serious novel?

Despite it's clear ironic humor, how is Catcher
in the Rye NOT a serious novel?  It epitomizes the tragic rebellion and
ultimate depression of an overprivledged teenager who has finally hit the ceiling on his
dislike for "the system."

After working in both public and
private schools, I've seen that Holden Caulfield is not entirely unique (a fact which,
had he realized it, might have helped him).  He certainly isn't common, but too many
kids stuck in a private education feel the pressure of school administrators, parents,
and peers for so long, they forget, or worse, never come to know their own
identities.

This is Holden Caulfield in a nutshell.  While
the book is written from his own sardonic view of his world, the seriousness lies in the
truth behind his emotions, which are largely due to an upbringing he neither asked for,
nor had any support in.