A esto or este

Hola David

I didn't find that sentence in our lesson so I imagine you saw it somewhere else.

It should say:

A este libro le faltan dos páginas.

(not a esto libro...)

This means:

This book is lacking two pages.

It's a bit difficult because it's using the verb "faltar" which works similarly to "gustar", e.g. "A María le gusta el chocolate".

With faltar you will find an "a" in front of whatever or whoever is missing something, hence: "A este libro..." and then you have the pronoun for 3rd person singular, referring in this case to a thing that is masculine, not a person, however it works the same way, hence "le faltan" (like when we say "le gusta" for he/she likes) 

Here's a lesson on gustar in case you missed that one.

And here is a list with lots of verbs that operate like gustar. You will see "faltar" there. 

I hope it helps.

Saludos