The name is the first clue. Then there's the sign painted on the wall outside: "Alternative Books, Magazines, Ideas, Info." And finally there's the door, painted bright red. When you walk down the stairs to this tiny, musty basement shop, you're walking into another era: not the Disco Seventies; the Radical Seventies. For a quarter-century, Mayday Bookstore has been the gathering place/think tank for left-leaning Twin Citizens. About ten years ago the store left its home on Chicago Avenue and resettled on the eclectic West Bank. But the philosophies are just the same. Titles such as Feminism Is for Everybody: Passionate Politics and Labor's Untold Story peek out from the front window. Inside the store you can browse through shelves stacked high with tomes about solar energy, North American Indians, FBI conspiracies, the Middle East, and Mumia Abu-Jamal. Then there's the entire wall marked "Left Thought" and "Anarchy," filled with everything from photocopied pamphlets ("Nationalism: Working-Class Nemesis") to classics such as The Communist Manifesto, by Karl Marx and Friedrich Engels. And in keeping with the progressive policies espoused in its many volumes, the store remains a nonprofit, staffed only by volunteers.