问一下翻译

That reader can clearly understand the ideas the author want to convey after reading is waht makes a successful play book.

Therefore, a successful drama is what makes the readers clearly know the idea and theme expressed by the writer after they read it.

主结构是名次性从句，里面有宾语从句和定语从句，把楼上的understand改成catch更地道，waht改成what,reader改成readers可以说就完善了。
That readers can clearly catch the ideas and themes the author want to convey after reading is what makes a successful play book.