This book continues the plot threads left dangling on the first volume, and it does a great job of following through and expanding on the events from the first book.
This second volume is, in many ways, stronger thant he first. The storytelling is more focused, less wordy, and moves at a slightly faster pace. The first volume, while having its share of big events and action, was slower and more wordy, probably to allow the reader to better understand and interiorize the cosmic concepts that are essential to understand the plots and threats the JL is faced with. Now that there is less to explain, the stories become more focused and immediate, while still presenting its share of high-concept cosmic plot threads and additions.
The Sixth Dimension arc, in particular, is excelllent.
The artwork is, much like in the first volume, by Jim Cheung and Jorge Jiminez. And while both are very good, Jiminez's artwork is sublime. So dynamic, so stylish, and so expressive. Its just fantastic.
Bare in mind, Scott Snyder's whole Justice League run should really be viwed as one long big story. While there are many twists, turns and adventure, there is never a real resoulution until its end (or so I assume, considering these two volumes, altough I've heard that even then, alot is left dangling, only to be resolved the Snyder penned events Death Metal and year of the Villain).
Also, a good grasp of DC's multiversial concepts is really kind of necessary if one is to properly enjoy this run. A casual reader might find himself quite confused by all this weird concepts if he is not somewhat familiarized with what came before.
Onwards to volume 3. if it's as good as this one, I'll have a blast with it.