I got into Freeport via the free True 20 version of the now-classic Death in Freeport adventure. After having run games for 10 years, I was amazed at how much humor and horror the setting evoked, thus I obtained this book (and the very good Freeport True20 Companion also).
The layout and the quite usable map (not fold-out though, but on the inside cover of the book) are superb. The systemless descriptions of the different parts of town give me enough material to run a game very quickly yet leave enough room for adlibbing.
Also impressive was a whole chapter on the key elements of Freeport and how to change them if needed, with many options for different needs and different worlds.
Highly usable book, highly recommended.