"Esto" is indeed a demonstrative pronoun [meaning 'this' or 'this one'] - but you have used it [incorrectly] as a demonstrative adjective, i.e., you need to change it to read "este libro"...

Note too that "Este" can actually stand by itself, serving as a pronoun... Sometimes - particularly in texts which are several years old - you will see this word [when acting as a pronoun] written with a tilde: "Éste".

But be aware that in the [masculine] plural you have to say "Estos", both for the pronoun and for the adjective. "Estes" is not a Spanish word. [You will, however, come across estés - as a subjunctive verb; and if you require a plural form of "eastern", then say "... del este".