We wouldn't be surprised to see Jacob's dad go all Kevin Spacey at dinner someday. He's an "amateur ornithologist" (1.38) who hasn't published a thing, and while his wife's family owns a drugstore empire, dear old Dad seems to feel inferior and insecure about his own lack of success.
No one in his family appreciates him. His wife is glad when he leaves with Jacob for Cairnholm Island—Jacob hears her say she's glad that Jacob and Dad are leaving so she wouldn't have "two needy children to worry about" (3.123). Harsh, right? Thing is, though, even Jacob is regularly disappointed in his dad. Jacob doesn't want to work a "real job," but he wishes his dad had one all the same.
Although it's nice for Dad to accompany Jacob to Cairnholm Island, he does it only because Jacob's psychiatrist forces his hand. And this isn't the last time he outsources parenting to Golan—he even calls the doc for an opinion while on the island instead of making a decision himself. Plus, while he wants Jacob to be safe, he doesn't want it badly enough to actually go with him anywhere. Instead, he spends most of his days drinking at the bar. And while he hopes to do some bird watching for a new book, when a new ornithologist shows up, Dad gives up almost immediately because the other guy has fancy binoculars.
Yes, you read that right: Fancy binoculars prompt him to throw in the towel.
What upsets Jacob the most, though, is that Dad gives up on Grandpa (though to be fair, Jacob gives up on him, too). However, at the same time, Jacob feels badly about the way his grandfather treated his father: "How do you say I'm sorry your father didn't love you enough to your own dad?" (4.137), he wonders. Jacob and Emma leave Dad a note at the end of the book about how awesome Grandpa really was. Perhaps this will help him realize that his father was a good person, and maybe he can use this knowledge to motivate himself to try to become the same.