To be honest I'd love to see the size of a Codex that could properly explain the ins and outs of the HH. It would be bloody huge.
Descent of Angels is going to be really interesting I think. Not only because it is about the Dark Angels own private little Heresy but also because it is the first novel about a Legion that doesn't turn tratior (or not fully anyway). It's going to ruffle feathers though no matter what way you look at it.
I think Little Horus is going to stay loyal to Horus. He's in far to deep now, even if he did get away from the Sons he would be shot on site. Either that or he will be killed off in a later purge probably by Abbadon. Horus and Abbadon will get a little suspicous of his motives. He isn't embracing Chaos he's just still loyal to Horus. And once a tratior always a tratior so they will think he might og back to the Emporer.
One thing I really did like about Flight was when Qruze repainted his armour to Luner Wolves colors - I thought that was such a nice touch.
Just checked on the internet and apparently Legion is going to be about the Alpha Legion. And because I'm so nice here is the cover of the book which I found. It might be fake though.
Graham McNeils next book which is slated for Spet 08 is aparently going to be about the Adp Mech and their infighting so it should be interesting to see the HH universe expanded to the non SM organisations.
Still no word on anything Night Lords

Whats worse is that their isn't much call for it. There is a fair amount for Salamanders and Raven Gaurd though which is fair enough something needs to be done about them but we can't have the Night Lords being the only Chaos Legion not being featured.