Look Closer by David Ellis

Simon and Vicky couldn't seem more a wealthy Chicago couple with a stable, if unexciting, marriage. But with these two... absolutely nothing is what it seems. When a beautiful socialite is found hanging in a mansion in a nearby suburb, Simon and Vicky's complex web of secrets begins to unravel. A whirlwind affair. A twenty-million-dollar trust fund about to come due. A decades-long grudge and an obsession with revenge. Both Vicky and Simon are liars--but just who exactly is conning who? Prepare to question everything you think you know in this wickedly clever novel of greed, revenge, obsession--and quite possibly the perfect murder.