Hún hefði átt að lesa drögin betur, því lykilatriðin voru ekki nógu skýr.

Not in this sentence. In eiga að + infinitive, eiga is part of a fixed expression meaning to be supposed to, to ought to, or should.

So hún hefði átt að lesa does not mean she would have owned to read. It means she should have read.

This is a past, unrealized obligation: should have read.

Breakdown:

• hefði = past subjunctive of hafa
• átt = supine/past participle form of eiga
• að lesa = to read

Together, hefði átt að lesa is the common Icelandic way to say should have read or ought to have read.

A useful comparison:

• Hún á að lesa = she is supposed to read
• Hún átti að lesa = she was supposed to read
• Hún hefði átt að lesa = she should have read

Because lesa stays in the infinitive after að in the construction eiga að + infinitive.

The past meaning is already carried by hefði átt. So the main action verb does not need to be in a past participle form here.

That is why Icelandic says:

• hefði átt að lesa not
• hefði átt að lesið

Drögin is the definite form of drög, meaning the draft or the drafts, depending on context.

Important point: drög is grammatically plural in Icelandic, even when English may naturally translate it as singular draft. So Icelandic treats it like a plural noun.

Also:

• drög = draft, draft version, preliminary document
• drögin = the draft / the draft document / the draft text

Because Icelandic and English do not always package ideas the same way. The noun drög is commonly used as a plural form for a draft or draft material.

So even if the best English translation is the draft, Icelandic grammar still treats drögin as plural in form. This is something learners simply need to get used to with certain nouns.

Because betur is an adverb, and it modifies the verb lesa.

Here it means better in the sense of more carefully or more thoroughly:

• lesa betur = read better / read more carefully

Compare:

• betri = better, as an adjective
• betur = better, as an adverb

Since the sentence is talking about how she should have read, the adverb betur is the correct form.

Here því means because or for.

So:

• ..., því lykilatriðin voru ekki nógu skýr. means
• ..., because the key points were not clear enough.

This því is a conjunction, not the pronoun form you may have seen elsewhere. It is especially common in written or slightly more formal style.

Yes. Af því að also means because, and it is often more common in everyday speech.

So you could say:

• Hún hefði átt að lesa drögin betur, af því að lykilatriðin voru ekki nógu skýr.

That would mean essentially the same thing. The version with því sounds a bit more compact and written.

It is the definite plural of lykilatriði, meaning key point or main point.

It is a compound:

• lykill = key
• atriði = point, item, detail

So:

• lykilatriði = key point
• lykilatriðin = the key points

Because the subject lykilatriðin is plural, so the verb vera must also be plural.

Compare:

• Lykilatriðið var ekki skýrt. = The key point was not clear.
• Lykilatriðin voru ekki skýr. = The key points were not clear.

So voru is simply the plural past form of vera.

Because predicate adjectives in Icelandic agree with the noun they describe in gender and number.

Here the subject is:

• lykilatriðin = neuter plural

So the adjective must also be neuter plural:

• skýr

This can feel strange at first, because the neuter plural form does not have an obvious extra ending here. But it is the correct agreement form.

Compare:

• atriðið er skýrt = the point is clear
• atriðin eru skýr = the points are clear

It means not clear enough.

Breakdown:

• ekki = not
• nógu = enough, sufficiently
• skýr = clear

So literally it is:

• were not sufficiently clear

This is a very common pattern in Icelandic:

• ekki nógu gott = not good enough
• ekki nógu stór = not big enough
• ekki nógu skýr = not clear enough

This is normal Icelandic clause order: subject, verb, then the negative and the rest of the predicate.

So:

• lykilatriðin = subject
• voru = verb
• ekki nógu skýr = predicate phrase

It is a straightforward clause after því, and nothing unusual is happening with the word order here. For a learner, the main thing to notice is that ekki comes before nógu skýr, just as English says not clear enough.