他正在读一本由马克吐温所写的一本书在刚刚开放的图书馆的二楼的阅览室英语怎？

He was reading a book written by Mark Twain in the reading room on the second floor of the newly opened library.

英语翻译： He's reading a book written by Mark Twain in the newly-opened reading room on the second floor.