So Wrong, So Right by E.J. Masden

Nat never intended to have sex with her best friend’s husband, but now that line has been crossed and there is no going back. What starts out as an unexpected, never-to-be-spoken-about-again mistake soon turns into something more intense than Nat or Jed ever saw coming.
Blindsided by the overwhelming sexual chemistry between them, the guilt-ridden couple know they are on borrowed time and need to get it out of their systems, before Jed’s wife gets back from out of town.
But what was meant to be purely physical becomes much more, Nat and Jed are left needing to make a decision that will change three lives forever.