I believe this is just a compendium of past rules for mass consumption. Throw in some pretty pictures, print it hardcover & full colour and profit just like the "campaign book". GW will not change points costs for army X in a suppliment rulebook, that just isn't going to happen.
As far as I can tell the only thing worth checking out in this whole book is (a) how much does a BT or C:SM Stormraven cost? (b) what missiles do BT or C:SM Stormravens come with?
As I play DE & Chaos, neither of those questions are pressing enough for me to spend $40.