I'm not going to complain about the rules in the codex. I think that a lot of them seem over-powered but I haven't played against the book yet and so I can't say what an actual GK force will be like to play against on the tabletop. What I can say is that, after finally reading a full copy of this codex, it has possibly the worst fluff I have ever seen in a GW book. I didn't even read the big old fluff section at the beginning of the book. when i do I'm sure it will lead to more frustration. I am just talking about the fluff behind the units and weapons in the "rules" section of the book. some examples after only one read-through:

-- interceptor squad fluff says they don't wear terminator armor with their personal teleporters because it is "too bulky" for warp travel. yet they use the same wargear to shunt a dreadknight, and land raiders get a minor upgrade to get yanked through the warp by a librarian?

-- purgators use their brains to warp bullets and laser beams around corners? Apparently there was one person out there who thought that the movie Wanted was cool. and that one person wrote this book... also a very similar quote in the assassins entry that sounds like something taken from that awful movie.

-- librarians teach their acolytes "the six chants of denial, the seven words of life and death, the eight songs of battle, and the nine terrible spells that form the basis of all magick". sounds like next Christmas's BOLS caption contest waiting to happen. "the twelve days of the inquisition". also, when did the fluff switch to calling it magick instead of psychic power? and why the hell do they spell it "magick"?

-- another librarian entry gripe - since when did the empire of man get their very own black library? Sanctum Sanctorum sounds like a lame-named black library. a library of all of the spells ever made and info on how to fight the gifts of chaos? sounds just like the black library without being hidden in the warp guarded by solitaires. how did they keep that one safe from chaos when the black library is barely safe itself?

-- there are supposed to only be a "few score" purifiers anywhere in the universe, yet a single army could take up to 30 of them. wouldn't that be about half of the entire reserve of purifiers out there? also purifiers are dumb. they are just so "good" that their "goodness" burns up the bad guys?

-- little monkeys. I thinkt hese guys are dumb. they have little digital lasers (that piece of wargear that no SM player has ever, ever used that rerolls CC wounds) that just happen to be mini obliterators? where have those been all these years? oh right, no one but a monkey can make their fingers shoot out a multi-melta shot...

-- Eversor assassin - gets pumped full of a drug called "frenzon"?? really? that's the best name they could come up with for it? what would make our guy go into a crazy frenzy? frenzy..... frenzon. lame

-- Valeria's runes of destiny - supposed to be some runes she stole from an eldar that she doesn't fully understand. first off, eldar runes wouldn't work for a non-eldar who isn't attuned to the wraithbone. second, how can a rune she doesn't fully tab in to do something way cooler for her than any eldar rune does?

-- rad grenades. millisecond half-life? by the time the particles got out of the grenade they would be inert. milisecond half-life means that in 10 milliseconds, there would be less than 9% of the radioactive mass left... hardly enough to get through ceremite plating and reduce a guys genetically-enhanced toughness by 1.

-- needle pistol fires off a monomolecular dart imbued with the strongest poisons known to man? first off, how are you going to get just one molecule of poison to travel all the way to the enemy without hitting any other molucules along the way that would cause it to deviate from its path, causing it to miss completely? also, how is one molecule going to get through terminator armor, or even IG t-shirt armor? once it gets there, what is it going to do? kill off a molecule-wide swath of skin in the guy's body?

-- and finally, the one that really bugs me. the dreadknight. why oh why do we need the dreadknight? it looks dumb, its fluff is dumb and for some reason it counts as an MC because apparently the marines were feeling left out with only mechanical creations and needed a "monster". except that this particular monster is still just a mechanical thing, just like a dreadnaught. then we just stick a random marine on the front and say it's not as fragile as that one guy would be because of "an impenetrable force field surrounding the cockpit". really? we can make those? why doesn't everyone have one of those force fields??
on top of that, the fluff behind making the dreadknight is stupid. apparently only some marines can figure out how to control an exoskeleton, even with all of their training, enhancements etc. apparently no one else has them because the Grey knights somehow know how to secretly make crazy new weapons without mars ever figuring it out.
but the worst part is justifying the need for a dreadknight. the fluff claims that a dreadknight is there to fight a Deamon prince or greater deamon in single combat if there doesn't happen to be an entire GK army around to fight it. but why would that mean you need a dreadknight? isn't the entire fluff section just telling us that any one GK is a super-awesome psyker who can beat up deamons with his brain? just have your leader go fight one like in the special character's picture where he is fighting some giant demon by himself. doesn't look like he needed an exoskeleton with an impenetrable force field. the entire army has force weapons, crazy invul saves and can take weapons that could make them swing faster than the deamon or would on a 2, or whatever. any single dude in the army could take down a greater deamon with one swing if he got lucky.

so that's my thoughts on this dumb codex. I know I can't be the only one who thinks the fluff in this book just sucks. maybe some people like it still. I wanted to see what people thought. do you like the fluff? can you look past all of the dumb ideas and still enjoy an army of super-marines?