Transpecial is a first contact novel. It's also a novel about war and diplomacy - because those things are entwined in the concept of first contact with an advanced civilization.
Science fiction writers have explored first contact in many ways over the years. In Star Trek, it's a recurring theme. Novelists touch on it in a variety of ways. Arthur C. Clarke's "Rendezvous With Rama" introduces us to mysterious aliens who toss a generation ship into the solar system, apparently to see what we do with it.
In "Eifelheim," Michael Flynn has aliens crash land in Medieval Europe. They don't survive, but they change those around them. Vernor Vinge's excellent "A Deepness In The Sky" explores both contact between the human and the alien (in this case some very alien aliens indeed) and the conflict between different human cultures. I could not recommend this book and the related "A Fire Upon The Deep" with its sequel "Children of the Sky" more highly.
The thing with first contact is it inherently contains a lot of one of the most important elements in any story - conflict. The conflict in "Rama" is what to do with and about the alien artifact. In "A Deepness In The Sky" some humans want to work with the alien spiders, others to exploit - or even destroy - them. And, of course, let's not forget "The War of the Worlds."
Transpecial explores the conflict between the humans and the aliens - it's a novel about working out how to get along despite instinctive and biological differences. But it also carries the echoes of older conflicts...between human and human and between human and dolphin (and there's a contact story in there, too, albeit in the past). When does the different become the alien? And what will really happen when we come face to face with beings from another world? (If we ever do).
The concept of alienness I chose to explore most strongly is that of the "Uncanny Valley Effect." A simulation of humanity becomes more and more disconcerting the closer it gets to human. Different people are affected to different degrees. Some people find apes uncomfortable to observe. What if an alien race was at once so similar and so different that its very presence triggered human fear and aggression at an instinctive level? Hence the ky'iin...a peaceful yet powerful race that only seeks to explore...but when they come up against humanity, things go very bad, very fast. How do you fix such a problem? By making use of the alien within humanity itself.