This book contains three stories, along with profiles taken from the Blackest Night #0 special. The first story details the first Blue Lantern, Saint Walker, and his life before he was chosen to become the first of the hope-empowered Blue Lanterns.
This is easily the most powerful of the three pieces, with Johns doing what he does best with this kind of story - introduce a character in a way that recalls their history and lays their motivations bare at the same time. Walker's story is an epic one and you truly get a sense of how heroic he was even before he was chosen to be a Blue Lantern.
The next story by Peter Tomasi isn't strictly necessary but is rather amusing. It details the life of a young Mongul and how he came to realize that he would not ever share his father's power; he would have to take it.
We don't get a lot of deep insight here, what with Mongul being a power-hungry bully who wants to rule as much of the universe as he can. But it is the first tale I know of that shows us Mongul The Elder and how he acted as a father to his son, Mongul The Younger.
The final story is also the most confusing, offering us a brief glimpse of the Indigo Tribe and their power.
This is personal theory, but I think their power is a counter to the Orange Power of Avarice as Hope counters Fear. While the Orange Lantern has the power to drain energy way from other Lanterns (mineminemineminemine!), the Indigo Power seems to redirect it. We see the Indigo leader do something that causes a mortally wounded Green Lantern to smother himself with a ring projection, giving him a relatively more painless death and turn yellow energy back onto a Sinestro Corps member, causing him to flee as his own worst fears are made manifest.
It's rather hard to say since we can't understand a bloody thing any of the Indigo Lanterns say, their language being untranslatable even by the Universal Translator of a Green Lantern ring. Most of this story is told through the art and Rags Morales' darker style isn't quite capable of making the action clear without several read-throughs.
The Bad News: None of the stories here seem to have any direct bearing on the plot of Blackest Night so far. And our first glance at the Indigo Lanterns doesn't give us much more information than their profile which contains about as much information about the Indigo Lanterns as the Hitch-hiker's Guide did about the Earth.
The Good News: Except for the last story, they are all very good character pieces that add insight into various characters, particularly the Saint Walker piece.
The Verdict: Good read. Worth picking up.