Boken er på kinesisk.

Bok means book in the indefinite form.

• en bok = a book
• boken = the book

In Norwegian, the definite article is often attached to the end of the noun instead of being a separate word. So boken literally means book-the.

Because bok is a common-gender noun, and its singular definite form usually takes -en.

So:

• en bok = a book
• boken = the book

This is a very common pattern in Norwegian:

• en bil → bilen
• en stol → stolen

Er means is. It is the present tense of the verb å være = to be.

So:

• jeg er = I am
• du er = you are
• boken er = the book is

In Norwegian, the expression for saying what language something is written or spoken in is often på + language.

So:

• Boken er på kinesisk = The book is in Chinese
• Filmen er på norsk = The film is in Norwegian
• Brevet er på engelsk = The letter is in English

Even though English uses in, Norwegian usually uses på in this kind of sentence.

På kinesisk means in Chinese or more literally in the Chinese language.

Here, kinesisk is the language name used after på.

Compare:

• på norsk = in Norwegian
• på engelsk = in English
• på kinesisk = in Chinese

In Norwegian, names of languages are normally not capitalized unless they begin a sentence.

So you write:

• norsk
• engelsk
• kinesisk
• tysk

This is different from English, where language names are capitalized.

In this sentence, it functions as the language name in the expression på kinesisk.

Many language words in Norwegian have forms that can also look like adjectives. For a learner, the easiest thing is to remember the whole pattern:

• på norsk
• på svensk
• på kinesisk

So even if the form looks adjective-like, in practice you can learn it as the standard way to say in Norwegian / in Swedish / in Chinese.

Yes. Denne boken er på kinesisk means This book is in Chinese.

The difference is:

• Boken er på kinesisk = The book is in Chinese
• Denne boken er på kinesisk = This book is in Chinese

The second one is more specific and points out a particular book.

The word order is very straightforward:

• Boken = subject
• er = verb
• på kinesisk = prepositional phrase

So the structure is:

Subject + verb + expression of language

This is the normal word order for a basic statement in Norwegian.

You usually make a yes/no question by putting the verb first:

• Er boken på kinesisk? = Is the book in Chinese?

This is a very common Norwegian pattern:

• Boken er stor. → Er boken stor?
• Filmen er på norsk. → Er filmen på norsk?