У книзі шість сторінок.

The book has six pages.

Breakdown of У книзі шість сторінок.

• книга: the book
• у: in
• сторінка: the page
• шість: six

Questions & Answers about У книзі шість сторінок.

Why is it у книзі and not у книга?

Because у here means in, and after this preposition Ukrainian uses the locative case when talking about location.

• книга = book (dictionary form, nominative)
• у книзі = in the book (locative)

So книзі is the locative singular form of книга.

What exactly does у mean here? Is it the same as в?

Here у means in.

In many cases, у and в both mean in and are interchangeable in meaning. The choice is often made for easier pronunciation and smoother sound.

So:

• У книзі шість сторінок.
• В книзі шість сторінок.

Both are possible, though one may sound more natural depending on the surrounding sounds.

Why is there no word for is/are in the sentence?