Hi. After a year or so of what I've felt was a series of mostly poor releases, this book has been the shining beacon to look forward to for D&D campaigns. The supplement is almost entirely self-contained, much like the previous Tome of Magic, in that very few pieces of the book are useful to any characters that are not built directly from the three base classes presented therein. This is probably the largest drawback of the book, aside from the potential that like many D&D supplements, we may see little more from WotC on the subject of Martial Disciplines and Maneuvers in the future.
The highlights of the book are the three new base classes: Crusader, Swordsage, and Warblade. The Crusader has the most complicated system as far as having maneuvers available to him, but its class abilities make it a formidable character option for front-line offense. Swordsages are your "Wizards" of the Tome of Battle, as they have the most options in terms of maneuvers known and disciplines available. Warblades are the closest to traditional fighters, and would be a great class for someone who likes fighter-types but with a little more pizzazz.
You've got nine Martial Disciplines, each with a unique flavour. Desert Wind focuses on mobility and fire damage, Tiger Claw focuses on animalistic movements and attacks, Setting Sun emphasizes throws and trips in a very Judo-like fashion, as a few examples. Each discipline has about 20-30 maneuvers of differing levels, some of which get very powerful. The maneuvers include strikes, boosts, counters, and stances. Strikes are like one-hit spell effects, boosts are temporary bonuses to some attribute, counters are immediate actions that can be used, and stances are lasting effects that only end when you change stances or altogether stop that stance. The advanced maneuvers tend to look very overpowered, but when compared with spellcasters of equivalent levels, they are very much on par. Remember, 20th level spellcasters have a bevy of instant-kill spells at their disposal, 20th level Psions can create their own planes of existence, so being able to deal +100 damage on a single strike as a 20th level Warblade shouldn't be too out of line.
The feats and prestige classes are almost entirely self-contained. Most feats require some knowledge of a martial discipline; all of the tactical feats do. A few prestige classes require caster level prerequisites (Jade Phoenix Mage) or undead turning capabilities (Ruby Knight Vindicator).
As for the Nine Blades themselves, these are Weapons of Legacy that follows the rules of the book of the same name. It is nice to see a little revisit to that text, which I had assumed would quickly fall by the wayside. (Ironically, Weapons of Legacy was one of the recent books that really disappointed me.)
In brief, this book is wonderful if you're running a low-magic campaign with an emphasis on a more tactical combat. Even in a high-magic setting, this gives fighter types more flavour in their motions, so "advance, full-attack, full-attack" isn't the only thing they have available. It's not for everyone, but I'm certainly going to make good use of it in my campaigns.