Dawn of the Aspects tells two distinct tales -- the tale of Kalecgos and his struggle with the resolution to Cataclysm that saw all of the Aspects drained of their powers, and the dragonflights with out a purpose, and a much, much older tale of just how the Aspects and dragonflights came to be. It's a really good, if confusing at times, story in which Kalecgos desperately tries to find a new purpose for dragonkind, while simultaneously taking a journey to the past and seeing the story of Galakrond, supposed progenitor of all dragonkind.
As for Charge of the Aspects, the short story by Matt Burns takes place on the eve of Deathwing's downfall, and features the four Aspects, together with Thrall, trying to figure out just how to kill Deathwing once and for all. It's available for free on the official website, but this is the first time the story has been available in print -- and it honestly provides a pretty good framing point for Dawn of the Aspects as well. If you're interested in a physical copy of both of these tales, preorders are now open on Amazon as well as Barnes and Noble. The book is $12.50, and is slated to be released November 19, according to both websites.