IF you play the Chicago setting, you'll want this book. Even if you don't, and you want an idea of how it's done, you'll want this book. Even if you own the 1st edition. Because we've taken the Chicago setting and revised and updated it. Now other denizens of the World of Darkness are clearly present where they weren't before (Assamites, Ravnos, etc.) and this book corresponds directly with the werewolf supplement, "Under a Blood Red Moon", which, together, you could use to play a Werewolf-Vampire War scenario.
The second edition is post-Under a Blood Red Moon, and the situation is quite different. The quality - proofreading, etc - is much higher than the first. The section on Kindred politics in the back is worth reading, the information is useful in any Chronicle.
I had read Chicago By Night 1st Ed, but never bought it because I didn't feel I needed it. Considering the way that WW 2nd Ed products have thus far been going (ie, not very far in terms of the new and innovative), I was hesitant to say the least on this one. I am pleased to say that I'm pleasantly surprised at the ammount of change that the city has undergone. It's actually worth a 2nd Edition.
Chicago has changed. In the wake of the Werewolf cross-over scenario Under a Blood Red Moon, many of the city's KIndred have bitten the big Final Bucket, including her Prince. This has left Chicago in a state of turmoil and danger. Several new Kindred from around the world have flocked to the city, some of whom are interested in the Princedom itself. The face of Chicago has become that much more violent and dangerous with Lodin out of the picture.
Overall, the new characters are both varied enough and well-thought out enough in general. They present a not-so-unified city. Chicago used to have a style of endless dance to it's politics, but not any more. With upwards of ten contenders for Lodin's throne, things are getting very hot very quickly in the city. The Primogen are equally warring and fighting each other endlessly. Plus, there are Lupine on the outskirts of the city now.
My advice, buy it.