I'm not a reviewer, but as I've had this since the 15th I'll try to post something.
1. You're getting your money's worth - the page count of the books completely fills the box. A lot of the monsters in the third book are creatures from older source material that isn't in the SRD, like some yugoloths and stuff.
2. The first book is full of places and light on details. Concepts range from "cute" to "really original". None of this stuff is the slightest railroaded - it's the kind of place that adventurers could just explore and look for neat things to kill. There's lots of potential for role-playing and politicking, but it's not scripted - the GM will have to come up with stuff.
3. The Necromancer people didn't shy away from the more "adult" enterainments available in a city of vile debauchery. Fortunately, details are left to the imagination. But if you've got perverts for players, they'll disappear into the souk and never be seen again.
4. The second book has the more "dungeon-y" locations. These are chained together in a loosely-organized campaign plot, but I think it will want expanding or rewriting for most GMs. The flavor of these locales is excellent, I'd say. They make use of everything they could get from the SRD and then some, so the variety of encounter is pretty good for a city full of efreet.
5. The plot is, overall, free of railroading. I'm almost going to have to build some tracks for my players (who like riding the rails) to follow. Basically, get your players to settle on a goal and then make them figure out how to accomplish it.
6. If you don't want to do a full City of Brass campaign, you'll still have no problem using this material, even just as a place to wander in and buy stuff. But you'll be missing out.
All in all, if you like Necromancer stuff and don't mind writing your own material to develop the campaign further, this is for you. If you're hoping for something you can sit down next week and play, you might look elsewhere. I'm not regretting my payment, and I'm looking forward to running it.