Would a proper adult ignore the spilled milk under the fridge for weeks? Would a proper adult take three years to post a solitary Christmas card? Would a proper adult have decades-old underwear in active service? Mike Gayle is nowhere near being a proper adult—even though his 10th wedding anniversary is looming; his second child is due any moment; and in less than 24 hours he is going to be officially closer to 40 than he is to 30. Appalled by this lack of maturity, Mike draws up a To-Do list containing every single item he's been meaning to do but just keeps putting off. He's got a lot of stuff that needs doing. But unlike previous To-Do lists, he promises himself that this one will actually get DONE. And along the way, Mike will learn stuff about life (323), love (999), friends (1004), and family (9), and finally work out what it means to be a grown up (846).