(I bought the limited edition hardcover of Amethyst, which was signed and included a beautiful colour print by Nick Greenwood. I have read the book but have not yet playtested the game, so I will speak less to the rules and more to the worldbuilding and concept.)
Amethyst presents a rich world that has been developed down to the niggling, wonderful details. While reading the book I was delighted to come across "bubbles" detailing culture-specific hand gestures, and eating utensils in both fey and human cultures. These are details that are rarely thought about but which are essential to a truly immersive roleplaying experience. The stunning, professional artwork included throughout the book do excellent justice to this vibrant world.
What I really love about Amethyst is that it brings the mystique back to fantasy. Clerics are no longer a dime a dozen, but instead number less than 50 in the entire continent of Canam (North America)--and each is glorified for his or her amazing gift. Reports by confounded scientists describe how fey skeletons should logically collapse under their own weight. This is a world in which magic "almost takes an intelligent delight" in suspending the rules of science. And yet, though romance and idealism can flourish in Amethyst, these almost childlike delights are tempered with a mature side that incorporates history, politics, ideology, and sexuality.
Some may complain that science and magic do not "blend" in Amethyst. This, I believe, is exactly the point. The incompatibility of science and magic provides a wonderful thematic conflict that is much less black-and-white than the old "good vs. evil" conflict--though that still exists, too. And don't think that science is the bad guy in this world--both magic and science have their dark sides in Amethyst, whether that be the incorporeal evil mastermind Mengus, or the xenophobic city of Mann. Each also has its limitations: technology malfunctions in the very presence of magical creatures, and magic has been limited in power, with the most powerful spells being extremely difficult to earn. I see these limitations resulting in interesting and challenging situations.
I will dip into the rules aspect by saying a few words about classes. I find the class system in Amethyst highly organized while remaining open to many possibilities. It also makes a lot of good sense. On the fantasy side there are fewer basic classes than in standard D&D, but within each is an array of possibilities, each with its own advantages. For example, within the "Fighter" base class, there are "class focuses" such as Cavalier, Bowman, Juggernaut, Virtuous Warrior, and more. Add to this the eight classes of "Techa" (no class focuses for these) and there are actually far more class choices than is first apparent. An interesting feature is that for the prestige classes of Paladin and Ranger, the prestige class is actually slightly different depending on how you entered it. For example, a Paladin from a Monk would be different than a Paladin from a Fighter. Also, a Ranger from a Druid would be different than a Ranger from a Fighter. Once again, this makes excellent sense.
While Amethyst is a rulebook, it is also part fantasy novel. Little blurbs of narrative throughout the book show glimpses of the world "in action," as it were, as do segments of an ongoing narrative at the end of every chapter. I enjoyed reading every one of these, and in my opinion these are excellent tools for DMs, as they familiarize the DM with the world as it would actually be lived in.
Finally, while I can't say I speak for all female roleplayers, I can say that personally I appreciate the designers' attention to little romantic details such as cultural marriage ceremonies, and relationships between fey and non-fey. While male roleplayers might balk at the idea of roleplaying a romance, I have to say that it's something I think is lacking in roleplaying in general. After all, what great fantasy novel doesn't include a romance?
Overall, the game designers have created a game that is not only backed by a beautifully rich world, but also one that encourages more challenging, more engaging roleplaying--something that I've been looking for more of.