[Ralfp]

If you are looking for fiction, Lem's Solaris is good exploration "too alien" concept.

[Gammarays]

Both. It feels as though both could offer interesting perspectives on alien intelligence. Since there's so much we don't know, I assume many theories would be labeled as fiction to be proven otherwise.

[zorpner]

Lem's His Master's Voice is also in the same genre, but the section A New Cosmology from A Perfect Vacuum is much more specifically about this topic.