It’s not a short read, but it’s eye-opening from the engineering perspective that nuclear arsenals are wildly complicated beasts with on-going maintenance, like any machine.
EDIT: It’s also available as a documentary on Netflix Not as in-depth, but it covers the Damascus incident pretty well.
If you want to read more with some amazing technical details of the Titan silos, I highly recommend Eric Schlosser's book "Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety". It's a compelling read.
For supplemental reading, check out Command and Control: Nuclear Weapons, The Damascus Accident, and the Illusion of Nuclear Safety. By Eric Schlosser. A Pulitzer finalist.
There is also a documentary on Netflix(?) about the Damascus Accident, where a liquid fueled ICBM exploded inside the silo.
There was infighting between proponents of nuclear safety and proponents of nuclear readiness in SAC and Los Alamos. Some people wanted to have multiple independent safety devices to prevent accidental nuclear detonations or launches, others wanted nothing but a big red button to launch the missiles.
Command and Control by Eric Schlosser does a very good job of telling this story, as well as the story of a nuclear accident in Damascus Arkansas.
I'm really not sure why we're still alive.
Turns out the answer to your question is simply: luck.
I suggest reading Command and Control:https://toptalkedbooks.com/amzn/0143125788
Fascinating read that goes into how close we got to full scale nuclear war and how often accidents with nuclear weapons happened.
This is a useful companion piece to Eric Schlosser's recent "World War Three, by Mistake" in The New Yorker. (Hat-tip to /u/puck2 for posting that article to this subreddit.)
For those still not sufficiently alarmed, PBS will premiere the documentary Command and Control , in its American Experience series next week (Tuesday, January 10, 2017).
Yes, gun type. Extremely inefficient aparently. If anybody wants to read about broken arrows nuclear incidents and how close we were to triggering Cold War https://toptalkedbooks.com/amzn/0143125788