I have been reading the book Global Catastrophic Risks Edited by Nick Bostrom and Milan M. Cirkovic. It is pretty good. I think I was pointed in its direction by a mention of a conference on this forum. The book has each chapter written by a scholar in the field covered by the chapter. The first 7 or so chapters are about general principles around GCRs such as what constitutes one and how our biases impact our reactions to and assessments of them. Then the second half of the book goes into the specifics of different types of risk, super volcanism, asteroid/comet impactors, gamma ray bursts etc. In my opinion about 70% of the book is game able. I am not going to use the stuff on insurance risks and catastrophe for example. But the stuff on super volcanism though not useable for the Fall directly, can be used to examine the relics of other intelligences wiped out on gatecrashed worlds. The book has at the end of each chapter recommended reading for further exploration of the topic of the chapter and being an academic type work has citation references for the whole chapter.