In Chapter 3, we learn that Tom is wistful and obsessive, unrealistic and imaginative, and passive:
Tom goes into exquisite detail as he describes Courtney's beauty, grace, and smell, all of which reveals the extent of his obsessiveness. He admires her intellect and even her voice as she reads aloud. Through this description, Tom states multiple times that Courtney is "perfect." His crush on her consumes his mind, and yet he never tries to talk to her or ask her out. He simply keeps her at a wistful distance from him.
In addition, Chapter 3 reveals how Tom fantasizes constantly about how he could rescue Courtney in some amazing feat of daring and strength. There would be an earthquake, he muses, and he would sweep her out of the crumbling building and into safety. She would faint, and he would catch her. These unrealistic fantasies of Tom's are nevertheless full of incredible detail, revealing the depth of his imagination.
Finally, Tom's passiveness is hard to miss in Chapter 3. His own friend, Jeff, makes fun of him in front of their peers, calling attention to how Tom is in the "dumb group" in reading class. Tom gives no response and is still friends with Jeff! And of course, by keeping his crush a secret instead of attempting to get to know Courtney, Tom is content to sit passively by and live mostly in his imagination instead of in the real world.