Having just purchased it myself about two weeks ago, I'll tell you what I like about it.
The system is basically d20, but with a few elements smoothed out. I think they got rid of op-attacks, and I KNOW they got rid of feats (simply rolling them into special abilities for each class). There is a skill system, much simplified, rolling tumbling and balance into acrobatics, rolling spot and listen and search into perception, etc. The nicest touch is that Base attack Bonus and Hit Points have been replaced by Combat Skill and Endurance.
There are races and classes, but only on the most general level. There are seven "race/classes" and multiclassing is heavily discouraged. (For one thing, it goes against the Lone Wolf Setting premises; for another, it is a rather stratified milieu where organizations do not bandy their secrets willy-nilly.
The seven classes are
Brotherhood of the Crystal Star (Human, Sommlending/Durenese) - "northern" mages, who have access to ten main spells and about a dozen "words of power" but they have different levels of power they can add to these spells, and they burn Hit Points (Called Endurance) to do so.
Knight of the Realm (Human, Sommlending/Durenese) - fancy fighters with all sorts of horseback stunts and weapon skills.
Dwarven Gunner of Bor (Dwarf, Bor region) - about as good a fighter as a cleric, but with some phenomenal Flintlock Pistol and Rifle skills - they can do extra damage and all sorts of trick shots with Firearms only.
Kai Lord - if you read the game Books, you already know most of what they can do (the hunting, stealth, psychic combat, etc.) - again, broken into different levels of prowess.
Mage of Dessi - if you read the Grey Star the Wizard Books, you know THEIR abilities, too! Evocation (calling on the dead), Sorcery(firepower and sorcerous shields), Elementalism, Alchemy, etc. BEST part of all - they even replicated Grey Star's Staff, the one that shoots magic bolts! And all Mages of Dessi get one at a certain level! Mages of Dessi use a Willpower score instead of Endurence to cast their spells, and the Mages live about two and a half times as long as normal humans. Interesting, but I don't remember Dessi being tied storywise to the Shianti, but they do that here.
Telchos Warrior (Human, Telchos) - think Ranger/Barbarians, and you have the basic idea. I believe they are all Amazons (female) but I can't recall right now.
Shadakai Buccaneer (Human, Shadakai) - Rogues and Bards rolled into one, but with no spellcasting, only pseudo-magical abilities.
They have a very nice magic items and equipment section. My mind swirled with names like Laumspur potions, Rendalim's Elixir, Graveweed, and Sleeptooth; I thrilled to seeing stats for the Dagger of Vashna and the Sommerswerd. Items have a LOT more history and flavor going for them than in AD&D, or Castles and Crusades, or 3E.
The editing definitely needed work, but this is a property of Mongoose in general, as I was given to understand, and not endemic to one product. I heard that they delayed this product to re-edit it anyway, and reduce errors; even with this, I noticed an assortment of minor errors. (For instance, one place where even though they took pains to rename Base attack bonus "Combat skill", there was one place in the combat chapter where it STILL slipped through.)
There is a VERY good section on the geography, the continents, the regions, etc. of Magnamund, as well as a history that was comprehensive. The game takes place in MS 5000 (5,000 years after the creation of the legendary Moonstone), which is fifty years before the events in the first Lone Wolf book. To use a Star Wars analogy, you play in the Rise of the Empire era, when the old empires are decaying and in decline, even though they keep telling themselves they're in a golden age.
Great book, if you are a fan of Lone Wolf, and you and your group want to play in that world.