I purchased this book with great expectations, as many of the stories were written over a similar time to my favourite David Brin novels (Startide Rising, The Uplife War, Heart of the Comet).
These novels and the short stories in this book have a number of common themes, facing and usually overcoming adversity/conflict, hope for the future and a belief that we as a race will grow up and take more care of our environment and the other species that share it with us, these stories though have something of a sharper edge.
The tales are told in the first person, and most are told very effectively from an emotional point of view, allowing the reader to feel what the protagonist feels. David Brin manages to do this with an effectiveness I have rarely seen let alone exceeded (George R. R. Martin, in A Song for Lya, Dying of the Light and many other novels and short stories is the obvious exception).
While there are a few stories I would rate at three stars, there are many fours, the River of Time and an unusual parallel world storey stick out here, the five star one I must mention is The Crystal Spheres.
This story attempts to provide an answer to the question, if there are aliens why aren't they here. The answer it gives is highly fantastic, but does fit the facts: each solar system that can support life is surrounded at a distance by a sphere that can only be broken from the inside.
The story is set some significant time after we have broken out of our solar system, and coped with the problems it caused, in a time when we believe that we are the first race to make it to other stars and the impact of loneliness that we consequently feel as a race. It starts with the discovery of another solar system whose sphere is broken and the reaction of the human race.
When I finished reading it the hairs on the back of my next were standing upright, this is a moving tale I cannot recommend enough, and is sufficient reason to buy the book. If you know (and like) David Brin read it.