A new book usually promises something exciting, and here it does: the pages are crisp, and the worlds inside them are still undiscovered. The speaker seems happy at first, sitting alone with something fresh after what feels like a long wait. But the poem quickly turns toward the people around them. Groups gather, and the speaker never quite fits in with any of them.
The ending is the most telling part. The line "I was lost again" echoes the subtitle, so the feeling frames the whole poem. "Again" suggests this isn't new; it's a pattern. The speaker may feel lost in a social sense, or perhaps lost in the book as an escape, and the poem leaves that open.
The mood is quiet and a little wistful. The short lines and repeated rhymes (ages, pages; sitting, fitting) give it a soft, steady rhythm, like a sigh. It captures the loneliness of being surrounded by others, and the comfort and sadness of retreating into a book.