A full bookshelf not only provides a conversation piece for guests, but it also lessens the odds they'll pull out the tome that triggers the trapdoor to your shrine to Don Knotts. Build up book collections and safeguard secrets with today's Groupon: for $10, you get $20 worth of books and merchandise, plus a copy of One Minute Mysteries: 65 Short Mysteries You Solve With Science! at Reiter's Books.

Popular with great minds and big thinkers, Reiter's Books is DC's oldest independent bookstore. Stocked with scientific, medical, legal, and technical books, along with T-shirts, posters, and strategic brain games, Reiter’s Books preps shoppers for debunking the beliefs of neighborhood cult members. Pick up a copy of More Money Than God: Hedge Funds and the Making of a New Elite, which covers a history of hedge funds from their rebel beginnings to their role in defining the future of finance ($29.95). Pintsize conspiracy theorists may scoff at Moon Landing: Apollo 11 40th Anniversary Pop-Up and its three-dimensional pop-ups that chronicle early space endeavors, from international space competition through the many successful flights of the Gemini and Apollo programs ($29.99). Amateur pharmacists should flip through The Tarascon Pocket Pharmacopoeia: 2011 Classic Shirt-Pocket Edition and its wealth of vital drug information ($15.95). Reiter's offers regular author book discussions, free WiFi at next-door coffee shop Cupa Cupa, and an array of literature to keep jurors occupied during closing statements of political corruption trials.