Ég las bókina tvisvar í röð.

Las is the past tense of the verb lesa (to read).

So the main forms are:

• lesa = to read
• les = read / am reading
• las = read (past)

A learner often notices that lesa changes vowel in the past. That is normal: lesa is a strong verb, so its stem changes rather than just adding a simple past ending.

Because bókina is the direct object of the verb, and it is definite.

Here is the breakdown:

• bók = a book / book
• bókin = the book (nominative, often used for the subject)
• bókina = the book (accusative, used here as the object)

Since las is a transitive verb and the book is what was read, Icelandic uses the accusative form.

In Icelandic, the definite article is very often attached to the noun instead of standing as a separate word.

So:

• bók = book / a book
• bókin = the book
• bókina = the book (in the accusative)

That -in / -ina part is the definite article built into the noun.

Yes, bók is feminine, and that affects its endings.

The form bókina reflects several things at once:

• feminine gender
• singular number
• definite form
• accusative case

This is why the ending is not the same as it would be for a masculine or neuter noun.

Tvisvar is an adverb, and it means twice.

It does not agree with the noun or change for case here. It simply tells you how many times the action happened.

Compare:

• einu sinni = once
• tvisvar = twice
• þrisvar = three times

So in this sentence, tvisvar modifies the verb las.

Í röð is a common expression meaning in a row, consecutively, or one after the other.

So tvisvar í röð means not just twice, but twice consecutively.

That is an important difference:

• tvisvar = twice
• tvisvar í röð = twice in a row

Because í röð is an idiomatic phrase. Learners should usually memorize it as a set expression.

Literally, röð is related to the idea of a row, line, or sequence/order, so í röð gives the idea of being in sequence.

Even though you can analyze the words separately, in practice it is best to learn í röð as a fixed chunk meaning consecutively or in a row.

A learner may ask this because í can take different cases in Icelandic. In this expression, the form is röð, and the phrase is best treated as a fixed idiom: í röð.

The important practical point is:

• learn í röð as one expression
• use it to mean in a row / consecutively

At an early stage, that is more useful than worrying too much about the case mechanics of this particular phrase.

This is a very normal Icelandic word order:

• Ég = subject
• las = verb
• bókina = object
• tvisvar í röð = adverbial phrase

So the structure is basically:

Subject + Verb + Object + Adverbial

That said, Icelandic also allows other word orders for emphasis because it follows a verb-second pattern in main clauses.

For example, you could also say:

• Tvisvar í röð las ég bókina.

That sounds more like Twice in a row, I read the book.

Yes.

• Ég las bókina tvisvar. = I read the book twice.
• Ég las bókina tvisvar í röð. = I read the book twice in a row.

The second sentence adds the idea that the two readings happened back-to-back, not just at two separate times.

Normally, you should keep the subject pronoun in Icelandic.

So Ég las bókina tvisvar í röð is the normal full sentence.

Unlike languages such as Spanish or Italian, Icelandic does not usually drop subject pronouns in ordinary sentences. In conversation or special contexts, things can sometimes be omitted, but as a learner, it is best to include ég.

In a neutral sentence, Ég las bókina tvisvar í röð is the most natural order.

You may sometimes see different orders in literary style or for emphasis, but putting the object right after the verb is the safest and most natural choice for learners.

So this is the best default pattern:

• Ég las bókina tvisvar í röð.

rather than trying to move bókina later in the sentence.