Popular science author Mary Roach's (@mary_roach) books have tackled a wide variety of topics including sex, the afterlife, digestion and space travel. In her soon-to-be-released book Grunt, she takes on the curious science of humans at war, delving into combat medic training, stink bombs, genital transplant surgery, the war on heat, shark repellant and diarrhea as a threat to national security. Pre-order your copy of Grunt now!