Virginia Hamilton, author of The House of Dies Drear, tackles a painful part of history, slavery in the US. Since her grandparents were slaves, and she heard stories about slavery from them, writing about slavery must have been very personal for her. Most students today know that any discussion of slavery will come with a heavy dose of suffering and dread.
Here, Hamilton focuses on the hope that drove the people involved in the Underground Railroad to risk their lives for freedom or to promote freedom for others. So, maybe that's why the tone seems hopeful. Here's a quote from Hamilton that helps explain her tone:
The past moves me and with me, although I remove myself from it. Its light often shines on this night traveler: and when it does, I scribble it down. Whatever pleasure is in it I need pass on. That's happiness. That is who I am. (source)
This quote is a little tricky. You might be asking, how can she find pleasure in such a gruesome part of the past? Well, maybe by making sure that future generations know what happened. She enjoys helping young people, like Thomas, discover the mysteries of history. Like Thomas, all students of history have to deal with what they find there, whether it's dreadful, hopeful, or a blend of them both. Through her tone, Hamilton urges readers to learn both the dreadful and hopeful truths of history.