Ég er vanur að lesa í rúminu á kvöldin.

Here vanur means used to or accustomed to.

So Ég er vanur að lesa... literally means something like:

• I am used to reading...
• or more naturally in some contexts, I usually read...

A useful pattern is:

• vera vanur að + infinitive = to be used to doing something

So:

• Ég er vanur að lesa = I am used to reading

This does not mean the English past-habit I used to read. For that, Icelandic would normally use a different structure.

Because Icelandic expresses this idea with:

• the verb vera = to be
• plus the adjective vanur = accustomed / used to

So the structure is:

• Ég er vanur ... = I am used to ...

This is very common in Icelandic: ideas that English may express with one fixed phrase are often built with vera + adjective.

Here að is the infinitive marker, like English to in to read.

So:

• lesa = read
• að lesa = to read

After vanur, Icelandic normally uses:

• vanur að + infinitive

So:

• vanur að lesa = used to reading / used to read
  (in natural English: used to reading or used to reading habitually)

It is an adjective.

That matters because it changes for:

• gender
• number
• case in some contexts

In this sentence, vanur agrees with Ég when the speaker is male.

For example:

• Ég er vanur = I am used to ... (said by a man)
• Ég er vön = I am used to ... (said by a woman)

So a female speaker would normally say:

• Ég er vön að lesa í rúminu á kvöldin.

Because the adjective must agree with the speaker’s gender.

The forms are:

• vanur = masculine
• vön = feminine
• vant = neuter

So:

• male speaker: Ég er vanur að lesa...
• female speaker: Ég er vön að lesa...

This is one of the things English speakers often have to get used to in Icelandic: adjectives can reflect the gender of the person being described.

Rúminu is dative singular definite of rúm (bed).

The preposition í can take either:

• accusative for motion into
• dative for location in

Here there is no movement; it means in bed, so Icelandic uses the dative:

• í rúminu = in the bed / in bed

Compare:

• Ég fer í rúmið. = I go into bed / to bed
  (motion → accusative)
• Ég les í rúminu. = I read in bed
  (location → dative)

That is simply how Icelandic often expresses this idea.

English often uses no article in set expressions like:

• in bed
• at school
• at home

Icelandic frequently uses the definite form where English would not:

• í rúminu = literally in the bed, but naturally in bed

So this is normal Icelandic, not something strange or overly specific.

Á kvöldin means in the evenings or at night, depending on context.

Literally:

• kvöld = evening
• kvöldin = the evenings
• á kvöldin = in the evenings

This is a common way in Icelandic to talk about something habitual or repeated at a certain time.

So the full sentence suggests a regular habit:

• Ég er vanur að lesa í rúminu á kvöldin.
• I am used to reading in bed in the evenings.

Both prepositions can appear with time expressions, but á kvöldin is very common for in the evenings / at night as a repeated time expression.

A learner should mainly remember the whole phrase:

• á kvöldin = in the evenings

It is best learned as a set expression. Icelandic time expressions often do not match English prepositions exactly, so trying to translate word-for-word can be misleading.

Because the sentence is talking about a repeated habit, not one specific evening.

So:

• á kvöldin = in the evenings / at night regularly

If you were talking about one specific evening, the wording would be different.

The plural here helps create the sense of something that happens habitually.

The sentence is:

• Ég = I
• er = am
• vanur = used to / accustomed
• að lesa = to read
• í rúminu = in bed
• á kvöldin = in the evenings

So the structure is roughly:

• Subject + verb + adjective + infinitive phrase + location + time

Very literally:

• I am used to read in the-bed in the evenings

More natural English:

• I am used to reading in bed in the evenings

Yes, depending on context, that is often a good natural translation.

Strictly speaking, vera vanur að means to be used to / to be in the habit of doing something. In real usage, that can overlap with:

• I usually...
• I’m accustomed to...
• I have a habit of...

So if the meaning shown to the learner is something like I usually read in bed in the evenings, that is perfectly understandable as a natural rendering, even if the Icelandic structure is closer to I am used to reading...

Yes. That would simply mean:

• I read in bed in the evenings
• or I read in bed at night

The difference is that:

• Ég les í rúminu á kvöldin states the habit directly
• Ég er vanur að lesa í rúminu á kvöldin emphasizes being accustomed to it or having it as a usual habit

So both are possible, but they are not exactly identical in tone.

A few very useful patterns appear here:

• vera vanur að + infinitive
  = to be used to doing something

• í + dative for location
  = í rúminu (in bed)

• á kvöldin as a time expression
  = in the evenings

Also remember adjective agreement:

• Ég er vanur... if the speaker is male
• Ég er vön... if the speaker is female

So this one sentence is good practice for:

• adjective agreement
• infinitives with að
• prepositions and case
• habitual time expressions