Well, I did it for Psychic Warrior, I may as well do it for Quintessential Druid as well!
The breakdown of contents looks something like this;
Character Concepts
The Prestige Druid
Tricks of the Trade
Druid Feats
Tools of the Trade
Living Magic
The Life of a Druid
Lords of the Terrain
The Otherworld
Druid Magic
Paths of the Shapeshifter
Sacred Groves
Just glancing through the Character Concepts and Prestige Classes, I see Child of the Wild, City Dweller, Oak Brother, Ollave, Rescued Soul, Nature's Brother, Unrebuked, Wandering Druid, Archdruid, Beast Whisperer, Dreamer, Grove Defender, Nature's Avenger, Noble Druid, Vitiate Maiden, and more.
Tricks of the Trade will allow you to track other druids across their natural habitat, using natural resources to craft items both magic and mundane, as well as using Ogham, the druidic language.
Living magic provides an alternative druid-only system for creating magical items charged with the forces of nature, or even enchanting trees and other flora & fauna, whereas the Life of a Druid focuses on their hierarchy and how indivduals can build their power and prestige (in more ways than one). Lords of Terrain gives details on how to move druids away from woods and forests - want a druid from a swamp? No problem. Savannah, prairie, steppe, ruins, coast, underwater, mountain, lake, desert - there are loads of them! Linking in with many druidic legends, the Otherworld gives details of another plane of existance, what it means to the druids, and how it can be utilised to fuel their growing powers. Using the rules in the Shapeshifters chapter, a druid can now assume the form of beasts, dragons, fey, oozes and even undead. Not always at low-level though
The Quintessential Druid wraps up with a look at Sacred Groves - how to create them, modify them, and defend them, something all druids will likely look at doing as they increase in level.
This is really just a quick flick through as, in all Quintessential books, there is a ton of new information about characters. However, I think druid players will much appreciate this book, and see it as a way to get their peers thinking of their characters in other terms than a 'forest cleric'.
Hope that helps!