It's subtitled "A true story of beauty and obsession" and a work of non-fiction about the Orchid industry and one of the more maniacal players in it (at least for most of the time Orleans was writing), John Laroche.
While I had no connection to the subject of the book (and found my interest waning at times as a result), I did find interesting the level of aforementioned obsession. A guy like Laroche may be a bit of a loon, but does provide good fodder for writing. Basic concept is a someone living to the extreme in life. Any project undertaken is going to be enormous, any failure the result of a grand conspiracy... and any moving away from something a complete abandonment.
It's reading about this extreme approach to life that made the book mostly worthwhile for me. I say mostly because if I had an interest in Orchids, I would have been more into the read... as it was, I liked it, but probably would have been good with simply reading her excellent New Yorker piece on Laroche the book came out of.