Fleishman is in Trouble by Taffy Brodesser-Akner

Toby Fleishman is newly separated and on the prowl. His job keeps him busy but not too busy to have sex with any female and see his two kids who he adores. While re-discovering himself sexually, which seems like he is doing with half of Manhatten, his ex-wife drops the kids off at his place and disappears. While she has never been the mother of the year, she is still taking care of the kids half the time and now has left Toby to shoulder all their needs 24/7. Summer camp helps as does a few days off of work but he still can't locate her so hence the book's title- he is in trouble. When he doesn't find her he must come to the realization that he has to make this work for his kids. All of this just makes him still ponder what exactly went wrong with his marriage, his work and his life. Sometimes you have to be thrown into chaos to find the important things.