This is probably one of the most unusual first contact stories that I have ever read. For a start, the story begins long after the aliens in question have been first contacted, on a planet long settled by humans.
Grass, a planet covered in swathes of multi-hued grasses with exceedingly long solar cycles and inhabited by strange creatures seemingly analogous to Terran horses, hounds, foxen and vampiric bats. Grass, with it's deeply isolationist policy and deeply entrenched class system, whose ruling classes know and care nothing about what goes on in the rest of the galaxy, the rest of the galaxy being just as ignorant about what goes on there.
But now Grass is becoming of the utmost interest to the rest of the humanity since a veracious and incurable plague is sweeping across the galaxy and only those on Grass appear to remain unaffected. Perhaps there lies a cure but the local aristocrats don't want outsiders there, only reluctantly agreeing to accommodate an ambassador and his retinue, charged with finding out if there is something about the place that makes people immune to the plague and if there might be a cure.
The story centres around the Ambassador Rigo, his wife Marjorie and family as they attempt to carry out their mission and wrestle with their own domestic troubles. But the story also encompasses a large number of other characters and this partly explains why the book is as long as it is. Marjorie soon learns there is a lot more to the indigenous life than they first thought and therein, somewhere, may lie the answer they have been looking for.
There is an important religious aspect to this story too, exploring some similar themes that James Blish explored in A Case of Conscience. Would intelligent alien beings be guilty of the Original Sin and how do you decide what is right and wrong? How should man see himself in God's universe if he is not the only intelligent (and soul baring) species?
This is quite a slow moving story but I still felt engaged throughout most of the book. I would have preferred it to be slightly shorter, with a somewhat more contained cast of characters but besides that, this was an excellent book.