The Devotion of Suspect X by Keigo Higashino

When Yasuko Hanaoka's ex-husband, Shinji Togashi, shows up at her workplace one day, she feels a mixture of fear and dread. In the past, Togashi has harassed her and she's given him money to leave her alone. But this evening ends with Togashi dead in her apartment after a tussle with Yasuko and her teenage daughter, Misato. Yasuko's next-door neighbor, Ishimagi (a brilliant mathematics teacher who has a crush on Yasuko), offers to help them with their situation. He concocts alibis for them and gets rid of the body. But Yasuko is Detective Kusanagi's prime suspect from the start. Yasuko's alibi seems solid, but the case takes an unexpected turn when physics professor Manabu Yukawa becomes involved. He's friends with Detective Kusanagi and consults with the police on cases. He also knows Ishimagi from college, even though they've lost touch. Soon the old friends Ishimagi and Yukawa are locked in a battle of the minds to either hide or find the truth. An engrossing book for fans of psychological mysteries like Karin Fossum. I hope more of Higashino's books are translated into English.