Om bibliotekarien hade visat mig den romanen tidigare, skulle jag redan ha skrivit min recension.

Yes. This is a counterfactual if-clause, meaning the speaker is talking about something that did not actually happen in the past.

• Om = if
• hade visat = had shown

So the first clause means if the librarian had shown me that novel earlier.

This structure is used when imagining an unreal past situation and its unreal result.

Structure here:

• Om + subject + hade + supine
• ..., skulle + subject + ha + supine

That is very similar to English:

• If the librarian had shown me that novel earlier, I would already have written my review.

Because Swedish is expressing a past event that happened before another past result in an unreal situation.

• visade = showed / was showing
• hade visat = had shown

In this sentence, hade visat is the past perfect, just like English had shown.

Using visade would not express the same clear counterfactual past meaning. For this kind of unreal past condition, Swedish normally uses:

• Om ... hade + supine
• ... skulle ha + supine

So hade visat is the expected form here.

This is the main clause of a past unreal conditional.

• skulle = would
• ha skrivit = have written

Together, skulle ha skrivit means would have written.

So:

• skulle jag redan ha skrivit min recension
  = I would already have written my review

This is the normal Swedish way to express the result of an unreal past condition.

Compare:

• Om han hade ringt, skulle jag ha svarat.
  = If he had called, I would have answered.

Because the if-clause comes first, and in Swedish the finite verb usually takes the second position in the main clause. This is the famous V2 word order.

The sentence is structured like this:

• Om bibliotekarien hade visat mig den romanen tidigare,
• skulle jag redan ha skrivit min recension

Since the first clause comes before the main clause, the main clause begins with the finite verb skulle, and the subject jag comes after it.

Compare:

• Jag skulle redan ha skrivit min recension om bibliotekarien hade visat mig den romanen tidigare.
• Om bibliotekarien hade visat mig den romanen tidigare, skulle jag redan ha skrivit min recension.

Both are correct, but when the om-clause comes first, Swedish uses skulle jag, not jag skulle.

Den romanen means that novel.

Swedish often uses this pattern for a demonstrative meaning:

• den + definite noun

So:

• romanen = the novel
• den romanen = that novel

If the speaker only meant the novel, then romanen would be enough. But den romanen points to a specific novel in a stronger way, like English that novel.

Because bibliotekarien means the librarian, not a librarian.

• en bibliotekarie = a librarian
• bibliotekarien = the librarian

The ending -en here is the definite form. Swedish usually attaches definiteness to the noun as a suffix.

So:

• bibliotekarie = librarian
• bibliotekarien = the librarian

In this sentence, the speaker is referring to a specific librarian, not just any librarian.

Yes. Swedish often allows a double-object pattern, similar to English show me the novel.

So:

• visat mig den romanen = shown me that novel

Here:

• mig is the indirect object: me
• den romanen is the direct object: that novel

You can also say:

• visat den romanen för mig

That is also grammatical, but visat mig den romanen is very natural and common.

Compare:

• Han gav mig boken. = He gave me the book.
• Hon visade mig bilden. = She showed me the picture.

Because redan is an adverb, and in this clause it naturally comes after the subject and before the infinitive part.

So the order is:

• skulle = finite verb
• jag = subject
• redan = adverb
• ha skrivit = infinitive + supine

This placement is very natural in Swedish:

• skulle jag redan ha skrivit

It corresponds well to English:

• I would already have written

You may also hear slightly different adverb placements in some contexts, but this is the standard and most natural order here.

Here tidigare means earlier.

So:

• den romanen tidigare = that novel earlier

In this sentence, tidigare works very well because the speaker is comparing one point in time with another.

You might sometimes hear förut, which can also mean before / earlier, but tidigare is especially common in this kind of neutral, written-style sentence.

So:

• tidigare = earlier, previously
• förut = before, earlier, previously

In this sentence, tidigare is the most straightforward choice.

Because the speaker is saying my review, not just the review.

• min recension = my review
• recensionen = the review

Swedish uses possessive words like min, din, hans, hennes, etc. before the noun.

Also notice that after a possessive, the noun is usually in the indefinite form:

• min bok = my book
• min recension = my review

You do not normally say min recensionen.

Yes. That would be:

Jag skulle redan ha skrivit min recension om bibliotekarien hade visat mig den romanen tidigare.

This means the same thing.

The main difference is word order:

• If the main clause comes first: Jag skulle ...
• If the om-clause comes first: ..., skulle jag ...

So both are correct, but Swedish changes the word order in the main clause because of the V2 rule.

It is completely normal and grammatically natural. It sounds fairly neutral and a little on the written side, mainly because of the full conditional structure.

A native speaker would understand it immediately, and it is a good example of standard Swedish grammar for unreal past conditions.

A more conversational person might sometimes simplify things in speech, but this version is clear, correct, and idiomatic.