I'll second all the positive things others have said previously. CSIO is a great product and it is very faithful to the original. The original is really the first large scale city that I remember being produced and it still holds up today. Yes, the descriptions may be bare-bones, but there is plenty there to work with. The whole idea behind it was to provide a framework for the DM (or Judge as the case may be) to build on and make his own (I think someone already said that). One difference for the above and below ground encounters seeming slightly different could be because they were originally 2 different products: CSIO and Wraith Overlord, which detailed the undercity. Necromancer seems to be trying to stay as faithful to the originals as possible in their JG remakes. The new maps are faithful as well, but nothing can beat the old brown, heavy stock maps of the original.
***oops, just read P. Lawinger's post...didn't mean to be so repetitive***