Answer:
Sorry, but your question is not complete and I could not find any online resource that had the passage you had in mind, but its really easy to find the theme of ANY book.
First of all, you need to find out what the book is talking about. Is it a book that talks about the consequences of war? Effects of famine? Importance or honesty? When you find out what the book is talking about, the next step becomes easy.
Next, and very important step is to find out the moral lesson the book is trying to give or what message it is trying to pass across.
With these two key points in mind, you can easily get what the theme of the book is.
N. B: A theme is the subject matter or focus of the book.
A theme can either have a theme of love, rejection, betrayal, patience, reverence, etc.
Good luck.