First, the book itself is just gorgeous. Its a big book too, which it should be since it covers several armies...more on this later. There's the typical Ultramarine focus, which is great since I play them but they did well to give Black Templar some space too since this is their codex too now. I'm sure that didn't please them, but of all the offshoot chapters, they were the best option. With the chapter tactics as they are now by simply having a few BT only units, they're covered. That's pretty much what their old book was anyway. You had a vow (vows, but only one good one) the Champion and crusader squads, but everything was really the same so now they're united. Of course the bigger book came with a bigger price tag, but if you didn't see that coming welcome to the hobby...grab some lube at the door.
On to the rules we have the good and that is the new chapter tactics. They're no longer tied to a special character though some characters do affect them. Now, you say "this is a Salamander army" and it is. If you made your own chapter you pick which First Founding chapter they came from and that's the set you use. As for the rules they go from decent with Raven Guard to flexible with Ultramarines to downright awesome with White Scars. I think the propper use of these will really define the book. We also have the long-rumored grav weapons and I really see these as being very useful. I hope riptides and wraithknights enjoyed dominating the table while it lasted. Grav guns will bring them back into balance just like Tau toned down flying circus. Just maybe GW had a plan...though I doubt it. More likely it was "lets sell a bunch of big expensive stuff then sell the rock to their scissors" Whatever it is it will ecourage more rounded lists which is good.
...and the bad. Well for starters those repulsive tubbynators the interwebs exploded about the last few weeks turned out to be as underwhelming as their models. They have an assault version that Terminators do better and a shooty version that again can be done better elsewhere. We also ave the new anti-air tanks which I am again unimpressed. These are good at what they do but nothing else so if you're facing lots of flyers and skimmers go for it...if not pass.
Part 2 I wrap things up and give my opinions on how my army will face the new book. Since it's my opinion, it must be true.