One thing I admire so much about all the Tillerman books is the way that the characters are so complex and rfull that they all stand alone. You could read this book without knowing one other bit about the Tillerman family, and it would still be a great book. But it's also in some ways the central book of this series — it shows you where everything else came from.
Theme and motif: several things going on here, at the same time. mildred_of_midgard pointed out the breaking and building motif. Bullet is a breaker; he doesn't build; Patrice also tells him he's not a builder. His brother John is a builder, John says. And Bullet shoots OD, and isn't able to rescue his mother… It's a hard book. But… Bullet, of all three of the Tillerman children of that generation, comes to a point where he accepts his life, which it's not clear the other two have done (they certainly had not come to that point when they left the Tillerman family).
There's also a pronounced racism arc, which interestingly carries over in a big way into Stranger, although it's a completely different thing in Stranger, of course.
There's also a boat again, in a confluence of boat and gift — Patrice makes Bullet a boat, as a gift (Bullet pays him for it, but it really is a gift), and Bullet gives it to Abigail — and that boat gives her a way to separate from her husband (I mean, not literally, more's the pity, but at least to manage that relationship with slightly more grace).
There's no music in this book, except square dancing from the jukebox (which is a very temporary and superficial form of connection, though connection nevertheless), and Bullet's and Abigail's memories of Liza singing, which connect them to her memory and really nothing else (well, maybe Bullet and Abigail to a certain extent). His father has squelched all the music — that which, in this cycle, makes family and found family.
I guess, maybe, the theme is growing up? Identity? This is the only book so far where I feel like it's hard for me to get a handle on it, because it's a book that I think generally sort of defies description. Like Bullet himself. He's described as being alone and separate, a man of bronze, a hero who just happens to be underage at the time. But he's also written as having a really finely-tuned sense of other people in a lot of ways, although completely oblivious and/or flat-out offensive in a lot of other ways. Of course, most people are a combination of those two things (especially in adolescence), but not to the extremes that Bullet's written — quite frankly most of the scenes with Bullet and Abigail in them just completely baffle me, because they understand each other's laconic words and I have no idea what they're talking about. (Please enlighten me! What does Abigail mean when she says Bullet used to have a good sense of humor? What does Bullet mean when Tommy says he thought better of Bullet, and Bullet says, "No, you didn't"? I think the former is just that Bullet hasn't yet had the idea of cooking breakfast for Abigail — and I think the latter is Tommy thinking everyone is just like him, and therefore he didn't think better of Bullet — but I don't know.)
Bullet thinks a lot about boxes, the way we box ourselves in, and his epiphany at the end is that we all are going to have boxes, we just get to choose whether we have boxes that we're comfortable with or not. I think maybe the book really is about the way we choose what limitations we work with, and what we do within those limitations.
But really I don't really know what the book is about. It's about the Vietnam War and the way the fear of the draft permeates everything; it's about race relations (or the lack thereof); it's about running cross-country; it's about how authority perpetuates itself; it's about a kid from an emotionally abusive family who is himself kind of violent; it's about all those things but it's not really about any of them.
Also, wikipedia tells me that in Homecoming James (who Liza was pregnant with, last Frank had heard — about a year ago) is 10 and Maybeth is 9. So you know what happened is that as a result of seeing Bullet in this book ("Frank's mouth drooped down a little at the ends. 'If I had the fare, I'd go up there right now, tonight; I could use a dose of Liza.'" And on the next page: "'I wonder if… do you think Honey'd give me the money to get to Boston?'"), Francis went away and went to visit Liza, who had just had James a couple of months previously, and Maybeth was the result. I… did not realize it was possible to hate him more than I already did, but IN FACT IT IS. Although violence is not my thing I… am kind of cheering Bullet on when he wrecks Honey's car (although to be fair it isn't at all Honey's fault. But still). (ETA 8-12: Um. Yeah. That really sounds like I think violence against innocent people is totally okay... which no. I should have said that I feel a lot of empathy for Bullet, and I do, but "cheering" is a bit much, yeah. Thanks mildred.)