Right! «Э́ту кни́гу» is the accusative case, used for objects. «Э́та кни́га» is the nominative case form, used for subjects.
Would this mean that the book is familiar to me (I've heard about it), I am familiar with a specifix book (I see a book that I lost three years ago and on a bus, I happen too see it and exclaim that "I know that book!" Or woukd this mean that I have memorized all of the knowledge in the book in question?