Listen for the Lie by Amy Tinera

 Lucy and Savannah were best friends in small-town Texas. Then one night, after a wedding, Savannah is found dead and Lucy is found wandering around, covered in blood with a bad head injury. Everyone assumes Lucy killed Savannah but Lucy can't remember anything, thanks to the head injury. The police don't have enough evidence to arrest her, so she leaves her abusive husband, Matt, and moves to LA. When the story starts, it's 5 years later and Lucy has been invited back to her hometown by her grandmother (the one person who believes Lucy did not kill her best friend). She goes back and crosses paths with Ben, a podcaster who is investigating Savannah's death. Ben uncovers a lot of secrets in the town but still can't prove what happened to Savannah that fateful night. Then something triggers Lucy's brain and it all starts coming back...

Quite the nail-biter.