I think you and brazil84 may have different notions of summarizing in mind. If summarizing a book means describing what's in it then most books can be summarized in a few paragraphs. If it means conveying a large fraction of the useful or interesting content then many books can't. (A dictionary or encyclopaedia might be an even better example than a physics textbook.)

Yes, I think so. Here is how I would summarize an unabridged dictionary:

This is a book which contains entries for most of the words in the English language; each entry sets forth the typical pronunciation as well as definitions for the word. Here are a few examples:

Example 1:

Example 2:

Example 3.