kono heya ha sizuka da si, eki ni mo tikai node, kanari kiniitte imasu.

Because 静か is a na-adjective (also called an adjectival noun), not an i-adjective.

In plain form:

• 静かだ = is quiet
• 近い = is close

So in this sentence:

• 静かだし = it’s quiet, and...

You need だ here because 静か cannot stand by itself as a plain predicate in this position.

し is used to list reasons or give multiple supporting points.

So:

• 静かだし、駅にも近い = It’s quiet, and it’s also close to the station

It often has the feeling of:

• for one thing...
• and also...
• plus...

It can also imply there may be other reasons too, even if they are not said explicitly.

Yes, but they do different jobs.

• し connects one reason to another reason.
• ので connects those reasons to the conclusion.

Structure:

• 静かだし、駅にも近いので、かなり気に入っています。
• It’s quiet, and it’s also close to the station, so I like it quite a lot.

So:

1. し = links reasons together
2. ので = gives the overall because/so connection to the result

This is very natural Japanese.

近い normally takes に when saying something is close to a place:

• 駅に近い = close to the station

The も adds the meaning of also.

So:

• 駅にも近い = it’s also close to the station

This matches the earlier reason:

• It’s quiet
• and it’s also close to the station

Because 近い describes a relationship of proximity to something, and the standard particle for that is に.

Examples:

• 学校に近い = close to the school

• 海に近い = close to the sea

• へ is mainly for direction (toward)
• から means from

So 駅に近い is the normal pattern.

Because 静かだし is not the end of the sentence. It is a non-final clause.

In Japanese, subordinate or connected clauses often use plain forms, even when the whole sentence ends politely.

So this is normal:

• この部屋は静かだし、駅にも近いので、かなり気に入っています。

The sentence ends politely with:

• います

This kind of mix is very common:

• plain form inside the sentence
• polite form at the end

It is polite overall because it ends with います.

Even though it contains plain forms like:

• 静かだ
• 近い

that is normal before connectors like し and ので.

So the style is:

• polite sentence ending
• plain subordinate clauses

This is extremely common in everyday Japanese.

Both can mean because or so, but ので is usually:

• a little softer
• more explanatory
• slightly less direct

Compare:

• 駅にも近いので、気に入っています。
  • softer, explanatory
• 駅にも近いから、気に入っています。
  • more direct, conversational

In this sentence, ので fits well because the speaker is calmly giving reasons.

かなり means something like:

• quite
• rather
• pretty
• considerably

So:

• かなり気に入っています = I like it quite a lot

It is stronger than something like ちょっと, but not necessarily as emotional as とても.

Depending on context, かなり can sound fairly strong.

気に入る means to come to like / to be pleased with something. In practice, 気に入っている often expresses the current state of liking something.

So:

• 気に入っています = I like it / I’m very pleased with it

This is similar to other Japanese verbs where -ている describes a resulting state.

It does not necessarily mean I am in the middle of liking it. Here it means the speaker currently likes it.

Both can express liking, but the nuance is different.

• 好きです = I like it
• 気に入っています = I’m pleased with it / I’ve taken a liking to it / I like it a lot as something I chose or evaluated

For a room, apartment, item, design, etc., 気に入る is very natural because it often suggests:

• personal approval
• satisfaction
• favorable impression after considering it

So for a room, 気に入っています sounds very natural.

Japanese often leaves out subjects when they are clear from context.

Here, 気に入っています strongly suggests the speaker’s own feeling, so the natural interpretation is:

• I like it quite a lot

So the omitted subject is understood as I.

は marks この部屋 as the topic of the sentence.

• この部屋は = As for this room...

Then the speaker comments on it:

• it’s quiet
• it’s close to the station
• I like it quite a lot

Using は is very natural because the room is what the sentence is about.

Usually は is better here.

• この部屋は presents the room as the topic and then describes it.
• この部屋が would sound more like you are identifying which room has these qualities, or contrasting it with others in a more specific way.

Without a special context, は is the normal choice.

Yes, it could.

• 静かで、駅にも近いので... = It’s quiet and close to the station, so...
• 静かだし、駅にも近いので... = It’s quiet, and also close to the station, so...

The version with し has a stronger feeling of listing reasons or building a case. It can sound slightly more conversational and nuanced.

The て-form version is more straightforwardly descriptive.

That sentence would simply mean:

• This room is quiet and also close to the station.

But the original sentence goes further and adds the speaker’s evaluation:

• so I like it quite a lot

So the original sentence is not just describing the room; it is explaining why the speaker likes it.

Not exactly.

Depending on context, し can feel like:

• and
• besides
• plus
• for one thing
• since

Its main role is to present one reason or point among others.

So in this sentence, a natural understanding is:

• It’s quiet, and it’s also close to the station, so...

But grammatically, it is doing more than a simple and.

Yes. It sounds like the speaker is giving reasons to justify their positive opinion of the room.

The flow is:

1. mention good points
2. conclude with personal approval

Because of し, it can also suggest:

• these are not the only good points
• there may be other reasons too

So the sentence has a natural, persuasive feel:

• It’s quiet, it’s also near the station, so I like it quite a lot.