The ending of this story is pretty much the happiest thing ever. The Tillermans have spent the entire book fighting and struggling to survive while nearly every single person they meet either abandons, ignores, or tries to control them. Then finally (finally) something good happens:
"Well, you should," Dicey said fiercely. "You should let us live with you."
That was no way to ask.
"Would that suit you?" Gram asked Dicey.
Dicey was shocked into silence.
"I thought you were the one it didn't suit," James said.
"Well, it doesn't," Gram said. "But it will. I give up. I do, I give up. You've worn me out. You can stay, you can live with me. You hear that, girl?" she called down to Dicey.
"Do you mean it?" Dicey asked.
"I don't say what I don't mean. You should know that." […]
"Ready to go home?" Gram asked Dicey. She was smiling.
Dicey just grinned back. "Ready," she said. (2.12.145-152, 162-163)
The last few lines hit on the most important theme in this book: the meaning of home. Gram's line is sort of casual, the kind of thing you might say to anyone after a long day out of the house—"Ready to go home?" But for the Tillerman kids, this means so much more. This is what they've been striving for this entire book, and now they finally have a place to call home. Whew.