It is a great book. Also, from my perspective City Campaigns are the easiest to run.
Players have a rather clear sense of place and personalities, and on the fly adjustments are very easy to do, it is much easier to move an inn from the Nobles Quarter to say the Tanners District, then recover from expecting the Party to go to Shadowdale and instead they go to Amn.
I wouldn't count on it. Monte is after all "Mr. 3rd Edition".One of the key things about Ptolus is that it's essentially an expression of the 3e rules. Monte Cook took the rules as physics and tried to extrapolate what a setting shaped by those physics would look like. I will be very curious to see how the world is modified by 5e rules, if in fact it is.
Also you got to keep track of many more NPCs and facilities than on the countryside.
That is game specific, Pixie Groves, Elven woods, Centaur plains, might have a great number of NPCs.
Being able to Speak w/ Animals via spell, race or other feature is not difficult so any game can turn into Bambi real quick.