Exhausting adventure
Valverde's Gold by Mark Honigsbaum, Farrar, Straus and Giroux, $25, ISBN 0374191700 Reviewed by Roy Herbert RESEARCHING a book on malaria, Mark Honigsbaum ran across the 19th-century English botanist Richard Spruce on his quest for cinchona trees, the source of quinine to treat the disease. Honigsbaum discovered that Spruce had also "stumbled on" a map …