This is the fourth in a line of mini-books from Mongoose, "Power Classes", each of which introduce a new core class. By mini-book, I mean basically like the various mini-modules from AEG and FFG - an 8 page regular sized book folded in half so it's 16 small or half pages. It's priced at $2.95. This details a class covered in many other d20 products, "The Noble".
There likely is a need for a "Noble" class, since there is an NPC class for "Aristocrat" in the DMG. And as mentioned, this class has been covered in products from WOTC themselves (like in Star Wars) and in products from other companies, such as Sovereign Press and Holistic Design. Because non-WOTC companies must follow by the d20 System Trademark License, and Open Gaming License, all their game mechanic stuff must be open, and thus the latter two companies Noble classes are open content.
Mongoose decided to not completely borrow a Noble Class from either of those two companies, but they did borrow a lot from Fading Suns d20.
The Mongoose Noble in this book is actually not quite like the Aristocrat Class in the DMG (the Fading Suns and Sov. Press Noble are essentially upgraded Aristocrats), but a bit different. It has the same (average) Base Attack Bonus, has 6 skill points per level (same as the Sovereign Press and Fading Suns Noble), but only had a d6 for hit dice, unlike all the others which has a d8.
What Mongoose mostly borrowed from Holistic was many of the "Social" Feats from Fading Suns d20. Fading Suns is something of a social intensive setting, so it introduced a new category of feat, called the "Social" feat. Mongoose does not borrow them as 'feats', but instead changed them into special abilities for the Noble Class. The Mongoose Noble gets to pick some of these feats as special abilities, and has several others assigned. By contrast, the Holistic Noble class has no special abilities, but gets a bonus social feat about as often as a fighter gets a bonus fighter feat. And thus can pick from a much wider range of feats.
So, while it borrows from Holistic, you lose a lot of the flexibility from their noble. Buying this book is a hell of a lot cheaper than buying Fading Suns d20 (by $22) though, and mongoose didn't do that bad of a job of it. They couldn't fit all the social feats from FS d20 into 16 half-pages.
The Mongoose Noble also seems to borrow a bit from the Sovereign Press Noble (though not 'officially', since it's not listed in Sec. 15 like Fading Suns is), in regards to having the Leadership feat given automatically, and having that enhanced as levels are gained. Still, the Sovereign Press Noble is more of the swashbuckling type - the main feature of that is the ability to add it's charisma bonus to it's armor class (though not in all armors).
So, comparatively, this is probably my 3rd favorite Noble. I like the Sovereign Press one the best, since I like the swashbuckling sort of Noble. The Fading Suns one is great if you want a social orientated Noble. The Mongoose Noble comes off as a somewhat watered down version of the Fading Suns Noble. Not terrible, but not great, either. However, if you don't have, or don't want to buy the Fading Suns book, or the Sov. Stone Campaign Setting book, and want a cheap Noble class, it's not too bad. I would probably alter the hit dice to a d8, like it's brothers (and it's cousin, the Aristocrat NPC class).
Besides the class, you get a new feat (Well Heeled) and a rather lame artifact, a sword that gives a charisma bonus but causes a catastrophe every year. Exciting, eh?
Ultimately, while I don't think this noble is all that great, and the new feat and magic item isn't great either, it's not bad. Decent resource for someone wanting a Noble class without buying a large book.