你可以读桌子上的这本书。翻译成英语

you may read the book on the desk

You can read the book which is on the desk.

注意，这里既然用定语从句了，就一定要有相应的主谓宾。

“Which”后“is”绝对不能漏。

You can read the book on the desk.
如果想更严谨一些，可以说 You can read the book which is on the desk.

you can read the book which is on the desk

you can read the book which is on the desk

you can read the book that on the desk.