Baker has come up with a variation on the "future do-gooders go back in time and meddle with history" theme, in which, in order to avoid paradox, the work is all done by people from the past. Children or teens who are about to die are recruited, modified physically so that they will live forever, and given assignments to preserve "lost" treasures from the past, which will later be "discovered" in the future by the Company. In this first episode, a girl known only as Mendoza is saved from the Spanish Inquisition and sent to England under Bloody Mary to preserve plants from a private gentleman's garden, the "Garden of Iden" of the title. She falls in love with a mortal, with disastrous and heartbreaking results.
The book is well-written in a direct, if not particularly artful, style. The characters and motivations are complex enough to avoid most of the usual cliches. In particular, Baker uses her scholarly knowledge of the Elizabethan era to depict the clashes between Catholic and Protestant forces in England with considerable depth and sympathy.
I haven't read any of the sequels, but if they measure up to this book, this series should be a source of considerable entertainment.