Learn Hardcore Japanese: tiisana katei ni site ha, hon ga ookute heya ga sukosi semai desu. - For a small household, we have so many books that the room is a bit cramped.

にしては after a noun means “for ~ / considering ~, (it’s surprisingly …)” and usually implies that the result is a bit unexpected compared to what you’d normally imagine.

小さな家庭にしては
→ For a small household, (it’s surprisingly …)

So the speaker expects a small household to have fewer books / more space, but the reality is different.

If you said 小さな家庭には, it would just mean “in a small household / as for a small household” without that “unexpected” nuance. にしては is specifically for “given X, the result is surprising / not typical.”

Why is it 小さな家庭 and not 小さい家庭? Is 小さな a different word?

Both 小さい家庭 and 小さな家庭 are grammatically correct and mean “small household.”

小さい is the normal い‑adjective form.
小さな is a special attributive form used only before nouns.

There is a small set of adjectives that have this “‑な” attributive version, mainly:

小さい → 小さな
大きい → 大きな

Nuance:

小さい家庭 is neutral and very common.
小さな家庭 can sound a bit more literary, descriptive, or slightly softer/poetic, but it’s still normal in everyday language.

You can treat 小さな simply as an alternative way of saying “small (noun)” before a noun.

What is the difference between 家庭, 家, and 家族 here? Why use 家庭?

These three are related but not the same:

家（いえ／うち） – the physical house or home.
家族（かぞく） – the family members (the people).
家庭（かてい） – the household / home as a unit and environment, including the family and the life there.

In 小さな家庭にしては, 家庭 focuses on the idea of a small household unit rather than just the building (家) or just the family members (家族). It sounds natural when talking about things like the lifestyle, number of possessions, etc.

What is the function of が with 本が多くて and 部屋が少しせまいです? Why not は?

In this sentence, が marks the subject / focus of each clause:

本が多くて – “(there) are many books”
部屋が少しせまいです – “the room is a bit cramped”

If you used は, it would sound more like you were setting up topics for contrast. With が, you’re simply describing the situation:

There are many books, and
The room is a bit cramped.

Also, having two は in such a short sentence (本は… 部屋は…) often feels heavy or contrastive (like “As for books… As for the room…”). Using が here keeps it more descriptive and neutral.

What exactly is 多くて here? Is it just “and,” or does it mean “so (that)”?

多くて is the て‑form of the adjective 多い (“many / much”).

Basic meaning: it links clauses, and its default translation is like “and”:

本が多くて部屋が少しせまいです。
→ “There are many books, and the room is a bit cramped.”

However, in context, the て‑form can also imply a loose cause-effect relationship:

“There are so many books that the room is a bit cramped.”
“Because there are many books, the room is a bit cramped.”

It’s not as direct as using から or ので, but Japanese often uses the て‑form to hint that one thing leads to the other.

Does 小さな家庭にしては apply only to 本が多くて, or to 部屋が少しせまいです too?

It applies to the whole rest of the sentence:

小さな家庭にしては、
本が多くて部屋が少しせまいです。

So the meaning is:

For a small household, they have a lot of books, and the room is a bit cramped.

Both having many books and the room being cramped are presented as somewhat unexpected given that it’s a small household.

What is the role of 少し before せまい? Is it necessary?

少し means “a little / a bit / slightly.” Here it softens the adjective:

部屋がせまいです。
→ “The room is small/cramped.”
部屋が少しせまいです。
→ “The room is a little bit cramped.” / “The room is somewhat cramped.”

It’s not grammatically necessary, but it changes the nuance:

Without 少し, the statement is stronger, more absolute.
With 少し, it sounds milder and more natural in polite conversation, avoiding sounding too blunt or critical.

Why is せまい used for the room instead of 小さい? Don’t both mean “small”?

Both relate to smallness, but the usage is different:

小さい – “small” in a general size sense (small dog, small car, small child).
せまい（狭い） – “narrow / cramped / not spacious”; used for spaces and areas.

For rooms, houses, streets, etc., Japanese usually uses 狭い:

部屋が狭い – “The room is cramped / not spacious.”
道が狭い – “The road is narrow.”

部屋が小さい is possible, but 部屋が狭い is much more natural to describe a room that feels tight or crowded, especially because of many objects like books.

Why is 多い written as 多くて here instead of 多いです?

多くて is the て‑form of the adjective 多い:

Dictionary form: 多い
て‑form: 多くて

We use the て‑form to connect it to the next clause:

本が多くて部屋が少しせまいです。
→ “There are many books, and the room is a bit cramped.”

If you used 多いです, you’d have to end the sentence or make two sentences:

本が多いです。部屋が少しせまいです。
→ “There are many books. The room is a bit cramped.”

Using 多くて makes it one smooth sentence and can also hint at a cause-effect relationship, as mentioned earlier.

Could this sentence be reordered as 本が多くて少し部屋がせまいです? Would that be okay?

You could say 本が多くて少し部屋がせまいです, and it would be understandable, but it sounds a bit awkward. The natural grouping is:

部屋が少しせまい → one chunk: “the room is a bit cramped”

Putting 少し right before せまい makes that connection clear.
少し部屋がせまい is not wrong, but 部屋が少しせまい is more natural and standard word order:

[subject] が
- [degree adverb] + [adjective]

Is the comma after は (in 小さな家庭にしては、) important? Do I always need a comma there?

The comma 、 is not grammatically required, but it’s very natural and helps readability:

小さな家庭にしては、本が多くて…

It shows a pause after the phrase 小さな家庭にしては, which is a kind of “introductory clause” (“For a small household, …”).

In spoken Japanese, you would naturally pause there, so writing a comma reflects that. In long or complex sentences, commas are especially helpful, but sometimes they’re omitted in short sentences. Here, including it is the most natural choice.

Why is the sentence ending with です and not だ? Does it change the meaning?

です and だ have the same basic propositional meaning (“is/are”), but differ in politeness level:

部屋が少しせまいです。 – polite (です/ます style)
部屋が少しせまい。 or …せまいんだ。 – plain / casual style

In this sentence:

…せまいです。 → Polite, suitable for speaking to someone you aren’t very close to, or in writing aimed at general readers.

The meaning (“the room is a bit cramped”) doesn’t change; only the register (polite vs casual) does.