Warcraft Chronicle Volume One was a really interesting book for any lore aficionados. While many of its revelations have since made it in-game, the book really laid down some firm information about the primary setting of the Warcraft games. We learned, for example, the fate of the Titans, why Sargeras went evil, what the Old Gods want, and what it is that really makes Azeroth so special.
Volume One focused entirely on the world of Azeroth and its pre-First War history. The opening of the Dark Portal is really the moment that the Warcraft calendar is built around, and thus Chronicle Volume One is all about "BDP," starting with the absolute beginning of Azeroth's history - when it was a planet whose powerful Titan World Soul was drawing too much of the Spirit element from the surface, thus leaving the indigenous elementals to war with each other without given the lack of that harmony-building essence. We go from that state all the way to the state of things prior to the First War.
Volume Two seems to be less linear. It appears to tell the stories of the First and Second Wars (the Third I'd bet they're saving for Volume Three) but it also leaves Azeroth to start examining the history of Draenor. (I'm hoping we'll see some stuff about Argus as well, but I don't know that we will.)
Draenor is of course the clear second-most important planet in the Warcraft games, as it is home to the Orcs, whose actions really define a great deal of the games' recent history.
In the sample pages previewed by IGN, we actually learn some interesting facts about Draenor.
Spoilers to follow.
The Titans, or at least Aggramar, did interact with Draenor, but unlike Azeroth, there was no World-Soul within the planet.
Interestingly, while Azeroth had particularly belligerent elementals, Draenor had unusually cooperative and peaceful ones. Now, perhaps the lack of any World-Soul whatsoever meant that there was nothing to siphon off the Spirit element, and thus it was all free to be used by the elementals, but it seems the Titans found plenty of worlds without souls, and Draenor seems to have been unusual even in this category.
Draenor was home to incredibly invasive plantlife that took the form of Sporemounds, which were massive mountains of organic matter that swallowed up basically all other living things in their path. Aggramar saw that these things would consume all other life on the planet, and in doing so they would even destroy themselves, and so he intervened. He created a massive giant to serve as his agent on the planet and fight back against the Sporemounds. This giant was called Grond, and if I had to guess, I'd assume that all the Magnaron, Gronn, Ogron, and later Ogres would descend from Grond. This is technically speculation, but we see the effects of this on Draenor. Grond destroyed the most powerful of the Sporemounds and later we see an ongoing war between the Breakers and the Primals.
As far as I know, there's no evidence of Old Gods on Draenor. But we do get some confirmation about the importance of the Curse of Sethe. We know that Arrakoa exposed to the blood of Sethe are cursed and twisted to become the Arrakoa we remember from way back in Burning Crusade. But in Chronicle, we get confirmation that this essence was weaponized by the Ogres to afflict the Orcs wit the Red Pox - a disease that killed many. Garrosh had this as a child and was thus sent to quarantine in Garadar, where this youthful weakness coupled with the Orcs' cult of strength really messed him up mentally.
There's no confirmation in these preview pages, but I'd suspect that the Horde would later weaponize Sethe's blood to create the Red Mist that mutated the Draenei into Broken.
It appears we'll be getting details about the formation of the Horde as well as an account of the events of the First and Second war as well as the fight between the remnants of the Horde on Draenor and the Sons of Lothar that ultimately ended in Draenor's destruction and transformation into Outland.
I've got to say, I usually turn my nose up at tie-in books (which is maybe just snobbery on my part, but oh well) but I make an exception for Chronicle. Not only is the book really attractive, it's also a really great comprehensive history for a really fun and interesting fantasy universe.