"Why is this book boring?"

Translation: Dlaczego ta książka jest nudna?

[Haxprocessor]

Dlaczego jest ta książka nudna? --> Wrong?

[luless]

When asking questions the word possitions are fixed:

(question word) + (subject) + verb + rest of the sentence.

You don't need question word or subject in every question: (Czy) (ty) Czytasz książkę? - (are you reding a book), Words in ( ) are optional, any configuration is correct.

In polish you don't need inversion or auxiliary verb.

A: Ta książka jest nudna.

B: Dlaczego ta książka jest nudna?

It is easy, isn't it?

[Haxprocessor]

Thanks. Yes, that's pretty simple. I just thought that Polish word order might be more flexible due to the case system.

[ChristineckaK]

Interesting. In Czech the order is flexible and the literal translation of "Dlaczego jest ta książka nudna?" (Proč je ta kniha nudná?) would be more natural.
It is fascinating how a language that is so similar can always surprise me :)