"In The Garden Of Iden", by Kage Baker, is the first volume in what looks to be an infinite series of novels about The Company - a standard, sf-style, shadowy entity whose own operatives know little about. Except these operatives are immortals, made so by time-travelling scientists, living through the past collecting rarities for sale in the future. Did I mention this is a historical romance set in Elizabethan England?
It's a good read, funny, exciting. Not bad for free.