Ok totally different topic: science fiction!
One of the classes I teach is astrobiology, and last year I had the students read/watch some work of science fiction that has well-thought-out aliens and then use knowledge from the course to critique those aliens.
@sundogplanets The Language of Power by Rosemary Kirstein definitely works, but unfortunately it's the third book in a series with the first two containing approximately no aliens (makes sense in context).
Greg Egan's The Clockwork Rocket and the whole Orthogonal series kinda works, but it's in a reality with alternate physics, so might be irrelevant from an astrobiology perspective in our universe?
Also paging @robryk , he is sure to have properly weird suggestions.
@timorl @sundogplanets
You meant The Lost Steersman (3rd book) as opposed to The Language of Power (4th book). Also, the second technically contains intelligent aliens, only the characters in it do not recognize them as such, and it contains some other alien life (hard to say whether characters recognize it as alien).
There's a spectrum of "humanness" that aliens in fiction display: with e.g. Solaris' ocean on one end (with its inscrutable thought processes) and (most of) Star Trek/Star Gate aliens on the other (with their social structure that one would not be surprised to find in some group of humans).
I think you are not after more realism (i.e. more towards Solaris) in this axis, but rather in terms of physical construction of aliens that should match the environment. Please tell me if I'm wrong.
Hal Clement is a good source of various kinds of socially very human-like (are always curious, have the concept of asking questions, form families/bands/...) aliens that live in weird environments. His stories concentrate on some aspects of the environment, and so the aliens might not be as fleshed out as you'd want (pun intended).
Some examples: Weirder/less concrete aliens: Foundling Stars sketches aliens that live at long timescales and large sizes. Proof sketches aliens that are made of plasma (or rather, of plasma currents) in stars (but it focuses more on the inferential distance between them and humans than on their composition). Uncommon Sense describes some aliens that live in vacuum and weird sensory apparatus they have (with very little attention paid to any other part of them). More concrete ones: Mission of Gravity describes aliens on a high-gravity, water-ammonia world. Close to Critical describes a water-based world where surface conditions are close to critical conditions of water with life on it. Planetfall describes aliens that perceive via vibration and EM wavelengths of VHF at the shortest.
I'm probably forgetting some other obvious authors, will think some more.