I haven't read Tales of the Black Kingdoms yet so can't rate that...
The GM Book for Shadizar boxed set is GREAT. (Keep in mind, since you seem from most posts to be a Howard purist, that about 1/3 of the city is inspired by a Robert Jordan pastiche which, while I hated the story and his portrayal of Conan, most of the NPCs were good and the city had a nice feel ala something out of Ali Baba or Tales of 1001 Nights, so their conversions in this book are good too).
I didn't really care for the adventure, but even if you don't you can easily use elements of it in your own adventures.
I don't remember what book 2 is--[edit: looked up Product Description]. I really like the way the city is described, laid out, the Jordan inferences on the Desert, the Merchants' Quarter, caravans, & etc. The boxed set also gives hints at the least about the other locations of Zamora for you to develop as you wish, often referencing the sources that inspired their location. The stats for NPCs & monsters may be very useful too.
I got the shoddy map with my boxed set (Dungeons & Dragons city with triangle islands and 120 degree square cut canal running through city) but was warned about it beforehand via this forum so expected it. Mongoose was great with the replacement map (see LBH's post first page about getting replacement maps). The counters are nice as well.
Overall Shadizar is pretty good, though I guess I'd have preferred a book format like Aquilonia or so, it was a gimick Mongoose tried twice so Vincent Darlage wrote it up to suit the format given him if I recall, thus 3 paperback books and counters. I plan on using it for the next campaign I'm getting ready to start, I really like most of it, and like even the least successful Mongoose release better than the best WotC releases (with a couple exceptions re: a couple of the adventures).
Here I'll post the product page for reference (I do it out of habit):
Anyways, hope this helps.