Це така цікава книга.

In this sentence, це means something like this or it is in English.

Ukrainian often uses це to introduce or identify something:

• Це книга. = This is a book.
• Це цікава книга. = This is an interesting book.

So in Це така цікава книга, це sets up the whole statement: This is / It is such an interesting book.

A useful comparison:

• Це така цікава книга. = This is such an interesting book.
• Ця книга така цікава. = This book is so interesting.

Both are natural, but the structure is slightly different.

In the present tense, Ukrainian usually leaves out the verb to be.

So where English says:

• This is a book
• The book is interesting

Ukrainian often says simply:

• Це книга
• Книга цікава

That is why Це така цікава книга has no separate word for is.

If you were talking about the past or future, you would use forms of бути:

• Це була цікава книга. = This was an interesting book.
• Це буде цікава книга. = This will be an interesting book.

Because книга is a feminine singular noun, and така must agree with it.

In Ukrainian, words like такий / така / таке / такі change form to match the noun’s:

• gender
• number
• case

Here:

• книга = feminine singular
• so the correct form is така

Compare:

• такий цікавий фільм = such an interesting film
  (фільм is masculine)
• така цікава книга = such an interesting book
  (книга is feminine)
• таке цікаве місто = such an interesting city
  (місто is neuter)
• такі цікаві книги = such interesting books
  (книги is plural)

For the same reason: adjectives must agree with the noun they describe.

Since книга is feminine singular, the adjective interesting must also be feminine singular:

• masculine: цікавий
• feminine: цікава
• neuter: цікаве
• plural: цікаві

So:

• цікавий фільм
• цікава книга
• цікаве питання
• цікаві книги

This agreement is one of the most important patterns in Ukrainian grammar.

Here така adds emphasis. In English, depending on context, you might translate it as either:

• such: This is such an interesting book
• so: This book is so interesting

In this sentence, така цікава книга most naturally means such an interesting book.

It is a stronger, more expressive phrase than just:

• Це цікава книга. = This is an interesting book.

Compare:

• дуже цікава книга = a very interesting book
• така цікава книга = such an interesting book

Both show intensity, but така often sounds more emotional or expressive.

Книга is in the nominative singular.

Why?

Because it is the noun being identified in a sentence of the type:

• Це книга.
• Це цікава книга.
• Це така цікава книга.

The basic dictionary form of книга is already nominative singular, so nothing changes here.

Also, the words agreeing with it are nominative singular feminine too:

• така
• цікава

So the whole noun phrase така цікава книга is nominative singular feminine.

Ukrainian has no articles.

English distinguishes between:

• a book
• the book

Ukrainian usually does not mark this with a separate word. Instead, the meaning comes from context, word order, or other words like цей (this) or той (that).

So книга can mean:

• a book
• the book

depending on the situation.

In Це така цікава книга, English needs an article, but Ukrainian does not.

Yes, Ukrainian word order is fairly flexible, but different orders change the emphasis.

The given sentence:

• Це така цікава книга.

is natural and neutral for This is such an interesting book.

Other possibilities include:

• Ця книга така цікава.
  Emphasis on this book as the thing being described.

• Така цікава книга!
  More like an exclamation: Such an interesting book!

• Яка цікава книга!
  Also exclamatory: What an interesting book!

So yes, you can change the order, but the feeling and focus may shift.

A useful stress pattern is:

• це
• така́
• ціка́ва
• кни́га

So: Це така́ ціка́ва кни́га.

A few pronunciation notes for English speakers:

• ц sounds like ts in cats
• и is not the same as English ee; it is a shorter, more central vowel
• г in Ukrainian is usually a softer sound than English g, closer to a voiced h
• stress matters and is not always predictable, so it is worth learning it word by word

Yes, but the meaning is slightly different.

• дуже цікава книга = a very interesting book
• така цікава книга = such an interesting book

So дуже focuses on degree in a straightforward way, while така often sounds more expressive or emotional.

Compare:

• Це дуже цікава книга. = This is a very interesting book.
• Це така цікава книга. = This is such an interesting book.

Both are correct, but they are not exact substitutes in tone.