The original book on time is still the best, says science journalist and author Charles Seife: “Einstein’s Relativity is so lucid, it really stands out. It’s incredibly clear, takes you step-by-step, and it’s very thin.” Newbie Stephen Hawking’s A Brief History of Time is less beloved. “I think lots of people bought it because of Hawking,” says David Harris of Stanford’s Linear Accelerator Center, “but I wonder how many actually got through it”—though the tenth-anniversary reissue is more readable.