Note that in the following question, the demonstrative pronoun this is not used as part of the noun phrase the book.
Is this the book you wanted?
This is the subject of the sentence. The book is the complement of the sentence. They are beside each other because of the subject/auxiliary inversion in the question form. They are not used together as a single phrase.
Non count nouns are used without an article to refer to something in general. However, sometimes an article is used to show a specific meaning
People all over the world want peace. (peace in general)
The peace was broken by group of passing children. (The peace refers to peace at a specific time and place.) The imparting of knowledge was the job of the elders in the community. ( knowledge in general)
A knowledge of computers is useful in many occupations.( a specific type of knowledge)