If you're devoted to explosions, and who isn't, you'll love the new expanded 2nd edition of William Gurstelle's Backyard Ballistics, now 25% longer, with 25% more ka-boomery. Still the go-to reference work for building rockets, cannons (carbide and potato), flingers, fire kites, electromagnetic pipe guns, tennis ball mortars, cleaner-bag balloons, ballistic pendula and petards. You simply can't have more fun with common household materials. The soft-cover, 210pp compendium includes detailed and illustrated instructions, parts lists and sensible ways not to be hoist on your own petard. Be careful out there.