Reddit reviews The Great North Korean Famine: Famine, Politics, and Foreign Policy

Here's my suggested reading list:

The Cleanest Race: How North Koreans See Themselves and Why It Matters

The Reluctant Communist: My Desertion, Court-Martial, and Forty-Year Imprisonment in North Korea

Escaping North Korea

This is Paradise!: My North Korean Childhood

White Tigers: My Secret War in North Korea (Memories of War)

The Tears of my Soul: An autobiography of the bomber of Korean Air Flight 858

The Great North Korean Famine: How and why it happened, and why it will happen again and again.

This hardly scratches the surface. I highly recommend the book The Greath North Korean Famine, which goes into the deep details. Here are a few more nuggets:

• Agriculture practices were a matter of state doctrine, immutable. Doctrine specified the distance between crops when planted, which were defined when North Korea was importing massive amounts of fertalizer. After the USSR collapsed and imports stopped, they didn't change these measurements, and massive crops failures resulted.
  
  
• A collapse in infrastructure. Without the oil and gas from Russia, North Korea was no longer able to maintain its existing infrastructure, particularly the rail system. So you had towns of people starving to death while rail cars full of food were rotting on the tracks, unable to go anywhere.
  
  
• Power shortages resulted in flooding of their coal mines, as the pumps that kept them dry no longer operated. So their source of self-provided power was hindered (by the way, wood-fire cars are common in North Korea), which only made things worse in a recursive manner. As for priorities in power consumption, I'm sure you've all heard about the dark cities where the only lights you see are the ones lighting up monuments and murals of Kim Jong {insert name here}.
  
  
• Without food provided by the state, people started growing their own private lots. Usually on hill sides, as North Korea is pretty rocky and most arable land was already in use. Without knowledge of proper irrigation practices on hill sides, they saw lots of soil corrosion moving soil from hill sides down into the rivers, resulting in flooding. This flooding further resulted in more crop failures.
  
  There were so many self-feeding factors that made bad things worse in a rapid way. It was a complex mess that you can only shake your head at.

Also keep in mind that that was also when North Korea was really starting to feel the economic downfall post-USSR. Before the Soviet Union broke up, the DPRK was almost entirely subsidized by Russia. All of North Korea's prosperity was imported. When the union fell, so did their support line. This was a large contributing part of what caused The Great North Korean Famine in which somewhere around a million people starved to death. The nation was clearly failing and defections began to skyrocket.

North Korea is more than likely in a 2nd great famine right now (but getting reliable data is almost impossible), so expect defections to continue to rise as reasons for leaving increases and the government's ability to control its border decreases.