I normally don't have high praises for pre-fabricated adventures or settings. However there are some products that are well made, and some nugget of inspiration can be found in almost anything. In this comment on JB's post in revamping Specularum, he alludes to the poor reviews that B6: The Veiled Society tends to receive. This module is not alone in receiving negative feedback. Many older modules are criticized for various reasons, lack of detail, no motivation for the villain, too cliche, etc, etc. Many of these criticisms are made in contrast to newer modules that promote "story" and "narrative" elements. I am not attempting to say that B6 or any other module is without flaws, yet many criticisms are laid at the feet of such works by those who don't seem to understand the core components of running a game or the inherent nature of a module. Running a module well will take more time and effort than creating your own content for the game; making someone else's content your own so that it fits your game will always be more difficult than creating your own material. Running a module poorly will also take more time and effort than pulling nonsense out of thin air during a session; the DM still has to take the time to read the module.
Back to the Module. As I mentioned, this module is by no means perfect. The building and npc cutouts are really unnecessary and rarely used, evidence of this is confirmed in my interview of my father about this module. It is space that could have been better used. The Radu narration reads like someone failed to become a writer and so snuck in their fiction in this module. The mystery is not fully explained in one single location or how the PCs can unravel the mystery. We can nitpick and point out flaws all day, so why do I think this is an example of a good module, especially for city adventures?
The primary virtue of this module is that it is short, yet also contains a lot of material for adventure. It is concise unlike many other adventures or rule books. We are told the vital information and nothing more. Concordant with this it is set up in such a way that the mystery and adventure unfolds in dramatically different ways every time it is played. It has replayability that unlike that available in a good dungeon. This module is a good example of what a module should be. It is easily placed in any campaign setting, yet still doesn't leave out details in order to be generic.
As far as the mystery goes; it is not difficult for the players to solve. There is no one point at which the players can be stumped and the DM has to take action for the 'plot' to continue. In fact, the PCs don't even have to follow the mystery. There has been only one group which I ran though this module that actually solved the mystery in the expected manner and followed the event structure laid out. There is so much variation of where the adventure could lead; there is no defined single outcome.
Lastly, what happens in this adventure will affect the state of affairs of the city afterwards. The players will be able to see how their actions directly influence the game world. They can ally with a single faction and become enemies with others, or they may stay aloof from all the factions and work for their own benefits. Whatever they choose the balance of power will shift.
And all of this is accomplished in 10 pages of adventure and 2 pages of background/DM advice.