"Я знаю эту книгу."

Translation: I know this book.

[pelayovial]

"эту книгу" changes the last letters of both words because the verb acts on "this book"?

[deactivated user]

Right! «Э́ту кни́гу» is the accusative case, used for objects. «Э́та кни́га» is the nominative case form, used for subjects.

[pelayovial]

thanks!

[Tunalord]

Why is it знаю and not знает? Is it singular vs pl??

[Derek642314]

Я знаю/ он/она знает

[duolingoHepCat]

Why is I do know this book wrong?

[Bona221879]

That extra DO would emphasize the sentence, like if someone was accusing you of not knowing it.

[IdeanBehfo]

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?

[IwantToLea20884]

All three meanings are possible

[RichardKeo2]

Your conclusions were all wrong, Ryan. Hallsey acted stupidly.

[breintje1]

Now there's a reference I haven't seen before