Water for Elephants is an historical novel, and a romance, there is sufficient "mystery" in the novel that I choose to include it on this website.
It is in my library, and is one of the best books I've read during the past five years. The author, Sara Gruen, was a technical writer who tried her hand as a novelist during National Novel Writing Month (nanowrimo.org).
At the center of this story is the elephant, Rosie, and Jacob, a former medical student who now looks after the animals in a traveling circus. Jacob falls for Marlena, the star performer, who is married to a nasty man, August, who is Rosie's nemesis.
Sara Gruen (prounced Groo' en) also wrote and published Riding Lessons (2004), Flying Changes (2005), and Ape House (2010).