Settu bókina upp á hilluna.

Settu is the singular imperative of setja, which means to put, to place, or to set.

So Settu bókina upp á hilluna is a command directed at one person: Put the book up on the shelf.

If you were speaking to more than one person, the imperative would normally be Setjið.

Bókina means the book.

It is made up of:

• bók = book
• -ina = the definite ending here, giving the book

It is also in the accusative case, because it is the direct object of setja: you are putting the book somewhere.

So:

• bók = a book / book
• bókina = the book

Hilluna means the shelf in the accusative singular.

Here is the breakdown:

• hilla = shelf
• hillan = the shelf in nominative
• hilluna = the shelf in accusative

It appears in the accusative because the preposition á takes the accusative when it expresses movement toward a destination.

So in this sentence, the book is being moved onto the shelf, not simply located there.

In this sentence, upp á works together to mean something like up onto or up on(to).

• upp = up
• á = usually on, onto, or at, depending on context

With something like a shelf, upp á is very natural because it suggests movement to a higher surface. English often says up on the shelf, and Icelandic does something similar.

So upp á hilluna means up onto the shelf.

Many Icelandic prepositions can take different cases depending on meaning. Á is a classic example:

• accusative: movement onto / to
• dative: location on

In this sentence, the book is being moved to the shelf, so Icelandic uses the accusative:

• upp á hilluna = onto the shelf

Compare:

• Bókin er á hillunni. = The book is on the shelf.
  Here hillunni is dative, because it describes location.

This motion-vs-location distinction is very important in Icelandic.

Yes, you often can.

Settu bókina á hilluna also means Put the book on the shelf.

Adding upp makes it feel more like:

• up on the shelf
• up onto the shelf

With a shelf, upp is very natural, because shelves are often thought of as elevated surfaces. But in many contexts, leaving it out would still be correct.

Because this is an imperative sentence—a command.

In Icelandic, commands commonly begin directly with the imperative verb:

• Settu ... = Put ...
• Komdu ... = Come ...
• Taktu ... = Take ...

This is similar to English, where commands also often begin with the verb:

• Put the book on the shelf.

So the word order here is very natural.

Yes. Setja is a very common general verb meaning put, place, or set.

It is often used when placing something somewhere:

• setja bókina á borðið = put the book on the table
• setja glasið hér = put the glass here

Depending on the object and the situation, Icelandic may sometimes use other verbs too, but setja is a very normal and useful default verb for put.

It is directed at one person, because Settu is the singular imperative.

If you were speaking to several people, you would usually say:

• Setjið bókina upp á hilluna.

So:

• Settu = command to one person
• Setjið = command to more than one person

Yes, Icelandic has some flexibility, but the version given is the most straightforward and natural for a basic command.

Settu bókina upp á hilluna is the neutral order:

• verb
• object
• adverb/prepositional phrase

You may sometimes see other orders for emphasis, but learners should treat this version as the standard pattern.

That would use a different structure because it describes location, not movement.

For example:

• Bókin er á hillunni. = The book is on the shelf.

Notice the differences:

• Settu bókina upp á hilluna.
  movement toward the shelf → accusative
• Bókin er á hillunni.
  location on the shelf → dative

This is one of the most useful contrasts to learn with prepositions like á.

A rough guide for an English speaker is:

SEHT-tuh BOH-ki-na uhp ow HILL-uu-na

A few helpful notes:

• ll in Icelandic is not always pronounced like English ll; its sound can vary and is often one of the trickier parts for learners.
• á is pronounced like ow in cow, but longer.
• u in Icelandic is not the same as English oo; it is a different vowel sound, though beginners often approximate it at first.

A more accurate pronunciation is best learned by listening to native audio, but this rough guide can help you get started.