Answer:
In Rick Riordan's novel "Percy Jackson & The Olympians: The Lightning Thief," after Percy's first night at Camp Half-Blood, he experiences a mixture of emotions. The specific textual evidence supporting this can be found in Chapter 5 of the book.
As Percy lies in bed, he reflects on the events of the previous day, including the battle against the Minotaur and the revelation of his true identity as a demigod. He is overwhelmed by the realization that the Greek gods and monsters are real, and that he himself is a part of that world. This is evident when Percy thinks to himself, "I'd had a pretty strange day myself. I had a lot to think about" (Riordan, 2005, p. 81).
Additionally, Percy feels a sense of isolation and loneliness. He misses his mother, whom he had to leave behind for his own safety, and he longs for a sense of normalcy. This is shown through his inner thoughts: "I had so many questions, and no one to talk to" (Riordan, 2005, p. 81).
Furthermore, Percy experiences a mix of excitement and apprehension about his new life at camp. He wonders what challenges and dangers lie ahead for him. This is evident when he contemplates, "I wondered what would happen to me next summer, whether I'd come back to camp and get claimed by my godly parent or get fried trying to fly back home" (Riordan, 2005, p. 82).
In summary, after his first night at camp, Percy feels overwhelmed, lonely, and uncertain about his future. These emotions are supported by the textual evidence provided from Chapter 5 of "Percy Jackson & The Olympians: The Lightning Thief."