Startide Rising is book two of the uplift series, the link above is to book one. The Uplift books are in the future, where humans have genetically engineered dolphins and monkeys to make them intelligent – to ‘uplift’ them. When they encounter galactic civilization, they find species all over the five galaxies are doing the same, uplifting others. Not all the aliens are satisfied that humans are themselves intelligent enough to be considered independent, some would like to see them assigned to another species for further uplift, some would like to see dolphins and monkeys reassigned to a more responsible species.
The first book sets the stage for this universe, the second has humans dealing with a political attack. Later books continue the story with new settlements and discoveries. The second book has the characters I found most sympathetic, which makes it my favorite.
This book addresses a lot of moral questions about the aims of uplift. For example, what amount of aggression in a species is an appropriate goal for the end of uplift? And who gets to decide, how much should say should the species being uplifted have? The same questions can be asked when we talk about cultural change in humans and it is fascinating.