a pile of books的用法和样例：
- A pile of books avalanched out of the shelf.
- He lifted a pile of books from the table.
- He pillowed his head on a pile of books.
- She had a pile of books in her mother desk.
- He knew where his heart lay, but where did his duty lie? And so did he toss and turn, and get up for a drink of water, and knock over a pile of books.