Dominick Birdsey is our cranky-as-the-day-is-long narrator of I Know This Much is True. Here is what we know is true about Dominick: He's angry. Here's a little round-up of why:
See? Dominick is one seriously disgruntled dude. As he tells us early on, "Never said I wasn't a son of a b****" (1.25), so brace yourselves to spend a whole lot of the book with him and his sunshiney ways.
Wally Lamb is rarely subtle with his character names, and Dominick is no different. Dominick means "belonging to God." Dominick was named after his grandfather, who practically thinks he is God, and Dominick is a chip off the old block, having plenty in common with the old man: anger management issues, a martyr complex, and misogyny.
It goes without saying (but we're still going to say it) that Dominick has anger management issues. Here's how he describes it: "I let stuff eat away and eat away inside of me and then—bam!—it just explodes" (2.265). Here's how we describe it: Dominick doesn't so much explode as pop off in a series of concentrated explosions, like a fireworks show in the middle of the night on a non-holiday when you're trying to sleep.
He likes being angry, saying that "Sometimes rage could feel as good as sex" (17.260). His anger repeatedly manifests itself as hypocritical passive-aggressiveness, like how he's always complaining about Thomas's selfishness (a valid complaint, honestly) but at the same time doing selfish things himself, like remodeling Ma's kitchen without asking her if she actually wants that.
Speaking of rage and sex being two sides of the same coin, we have to mention that Dominick has a habit of imagining that he's having sex with someone else while getting it on with his current partner. Here are just a few pieces of evidence:
This is a man who believes that the grass is greener (or at least that the booty is nicer) on the other side, and a man who is generally content being discontent.
Besides anger, Dominick's other predominant character trait is cowardice. He often says things like, "I was too gutless to object" (16.25), "I almost spoke" (20.74), and "I just wanted to get out of there" (22.207). He has no problem making things up about Ralph Drinkwater in order to get the cops off his back, and he even considers suicide for a few pages, but decides not to do that either, simply saying, "I couldn't do it" (32.31). So perhaps it's not so much cowardice as apathy that runs rampant with Dominick—as with his anger, Dominick prefers to stay the course.
Occasionally he tries to make some sort of moral stance, like when he says, "I didn't want to cash in" (11.6) on being beaten by the hospital guard. But he subsequently has no problem cashing in on his Native American ancestry, which he's known of for about ten minutes before accepting money from the Wequonnoc Tribe and becoming a millionaire at the end of the novel.
Despite his selfish the-world-is-out-to-get-me attitude, everything works out for Dominick at the end. This is because the world actually isn't out to get him, so despite his angry and apathetic ways, things still work out. He gets re-married to his first wife (despite still being an angry misogynist), ends up adopting a child, comes into a windfall of cash, and gets his dream teaching job. He does little to effect change, but change comes his way anyway.
The main source of Dominick's problems all along is that he's tethered to his twin brother, Thomas, who was Ma's favorite and who grapples with mental illness. Dominick says that Thomas is an "anchor" (17.273), but despite growing up together, the two don't seem to be all that close (in fairness, mental illness can do that to a relationship). Dominick alludes to some sort of twin telepathy at times, like how "Sometimes I know what Thomas is going to say even before he says it" (5.82), but he doesn't feel anything when Thomas dies. Except relief.
To be clear, then, the biggest change—the thing that perhaps sets all of the other changes in Dominick's life in motion—is Thomas's decision to kill himself. In doing so, Thomas un-anchors Dominick, freeing him to focus on himself unimpeded by his brother's needs. It's a tricky message about mental illness, to say the least.