I suspect most of us who have given it any thought have a favorite method of destroying the world. My favorite is a gamma-ray burst, because it's a death ray from outer space. Death ray from outer space! What's not to love? It's so unlikely it might as well be impossible, but it's so gloriously, stupendously inescapable and cosmic, the statistics don't concern me. I don't really want a death ray from outer space to obliterate the Earth's ozone layer and inundate every living thing on the planet with lethal radiation while turning the sky brown and plummeting the planet into a catastrophic ice age, but I love thinking about what a vast and unpredictable place the universe is, and how vulnerable we are as fleshy little blobs living here. If you do have a favorite method of destroying the world, or would like to acquire one for a conversational topic at cocktail parties, this book might be relevant to your interests:
Death from the Skies! The Science Behind the End of the World by Philip Plait
Phil Plait is probably best known as the author of the Bad Astronomy blog, source of wonderful astronomy information and news combined with ongoing, tireless criticism of creationists, climate change deniers, anti-vaccination crusaders, and many other species of anti-science idiots and their propaganda, of which the modern world has no shortage. (I considered and discarded several less kind words before settling on "idiots." We'll go with "idiots.") I enjoy reading Bad Astronomy, so I figured I would enjoy this book too, as it is on one of my favorite topics: how the universe is trying to kill us.
That's not a complete description of the book, to be honest. It is about how the universe is trying to kill us in many exciting and interesting ways, but in covering the numerous ways the Earth might be horribly destroyed, it is also a very good introduction to some of the most interesting aspects of astronomy and planetary science. The chapter on why it's a bad thing if asteroids hit Earth (just ask the dinosaurs!) is also about the structure of the solar system and the nature of planetary orbits; the chapter on solar storms is a stealthy introduction to solar physics. If nothing else, you'll come away this book with a proper, healthy respect for that terrifying cauldron of seething fiery power that rises and sets in our sky every day. The chapters on supernova, gamma ray bursts, and black holes contain great descriptions of the cycle of star life and death, and nearly all of them end in fantastic explosions. None of this stuff is anything we really have to worry about, but that's not the point. The point is that asking "What if...?" and playing out the possibilities is fun, and that understanding potential cosmic danger requires understanding how the universe works.
The only disappointing chapter was the one on the potential for an alien invasion, because it mostly rehashes the same old "they're out there" versus "if they were out there, they would be here already" argument that every other discussion of potential alien invasion has already gone over, without adding much that's new or convincing. I'm not sure why very smart people with vast amounts of knowledge are so bad at making the "if they were out there, they would be here already" argument remotely satisfying, but I suspect it has something to do with the fact that it requires astronomers and cosmologists to tread awkwardly into the fields of biology and, worse, highly speculative extraterrestrial psychology (is that even a real field of study? it should be) to discuss what aliens who might or might exist might or might not do when exploring the stars, and that's not something very many people are good at, at least not very many people who aren't exobiologists and/or science fiction writers. There's too little solid science, and it's too easy to think your way around the oft-discussed problems by applying a little bit of imagination.
On the other hand, my favorite chapter in the book is the last, the one about the eventual, inevitable death of the universe. It's a topic that is incredibly difficult to wrap your head around, involving time and space scales that are so far outside our comprehension they're little more than numbers with too many zeroes, and that's why I love it. The future it describes is so fascinating, so bleak and bizarre and stretching far beyond our ability to understand it, it's a perfectly weird and wonderful counterpart to the model of how the universe began. Our squishy human minds can't imagine that kind of emptiness, but maybe that's what makes it such an irresistible challenge to try.
Death From the Skies! (the exclamation point is right there on the book's cover; I'm not adding it for my own nefarious punctuational purposes) is a sneaky book. It lures you in with the promise of planet-incinerating explosions--and, oh, there are some glorious explosions--but also contains a lot of very good, solid science about the large structure of galaxies and the universe, how stars live and die, the best way to go about relocating a planet when it comes time to outrun an exploding star, and the precise anatomical details of the excruciating death waiting for you if you should ever fall into a black hole, which is something I've always wondered about but is, alas, rarely discussed in conventional physics texts. Now I know! I do love learning new things.