In the novel It by Stephen King, a word which describes the tone in this excerpt best is nostalgic.
<em>Nostalgic</em> refers to the sentiments or affections which are related to the past, specifically for a place or periods relating to a happy personal association.
In the above excerpt line which depicts nostalgic affection is
“The energy you drew on so extravagantly when you were a kid, the energy you thought would never exhaust itself—that slipped away somewhere between eighteen and twenty-four,”
Richie gets nostalgic when he enters the room and feel the energy that he used to as a kid.
I know the structure of the stories in the movie and book is different. I don't know comparison between the both, sorry.
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