A recount about life in Kowloon Walled City by a photographer who spent four years there during the 1990's. Includes photographs, interviews, and interesting essays.
Most of the reason there were any problems there at all was that there was no legal jurisdiction over it, there are still buildings in Hong Kong that have nearly that density with none of the legal issues.
Strongly recommended.
I highly recommend that you find a copy of this (in)famous book about it: << City of Darkness>> (https://cityofdarkness.co.uk).
The "no laws and/or regulations in KWC" is a bit of a myth though, HK police began patrolling the place in the early 70s, plus despite its legal status it benefited from HK's infrastructure, such as postal services or the electric grid. It was lawless mostly in its number of unlicensed dentists.
http://www.amazon.com/City-Darkness-Life-Kowloon-Walled/dp/1...
Note: There is a 2nd edition coming out soon (via Kickstarter)