Learn Hardcore Japanese: musume no itiban no syumi ha manga wo yomukoto de, maiban sukosi zutu yonde imasu. - My daughter's biggest hobby is reading manga, and she reads a little every night.

Using が (娘の一番の趣味が…) would sound odd here, because we’re not just identifying “what her hobby is” in contrast to others; we are introducing a topic and then talking more about it (she reads every night).

Typical pattern:

X は Y です – As for X, (it) is Y.
娘の一番の趣味は漫画を読むことで、… – As for my daughter’s number‑one hobby, it is reading manga, and…

So は fits the “topic + comment” structure of this sentence.

What is the role of を in 漫画を読むこと?

を marks the direct object of the verb 読む:

漫画を読む – to read manga
- 漫画 – manga
- を – direct object marker
- 読む – to read

Then 読む is nominalized to 読むこと (“the act of reading”), so:

漫画を読むこと – the act of reading manga / reading manga (as a noun phrase)

The を is required because 漫画 is what is being read.

Why is 読む changed to 読むこと? What does こと do here?

こと is nominalizing the verb; it turns a verb phrase into a noun‑like phrase:

読む – to read (verb)
読むこと – reading / the act of reading (noun phrase)

Since 趣味 (hobby) is a noun, what comes after は needs to be a noun phrase too. You can’t say:

✕ 娘の一番の趣味は漫画を読む。

You need something noun‑like:

娘の一番の趣味は漫画を読むことです。
“My daughter’s number‑one hobby is reading manga.”

So こと is used to make “to read manga” into “reading manga” (a thing, an activity).

Could you say 漫画を読むの instead of 漫画を読むこと? Is there a difference?

Yes, you could say:

娘の一番の趣味は漫画を読むのです。

In many casual contexts, Vるの and Vること are interchangeable as nominalizations.

Nuances:

〜こと – a bit more formal/neutral, slightly more abstract.
〜の – more conversational, sometimes feels a bit more personal or concrete.

In a sentence about hobbies, both work. In textbooks and more formal writing, you’ll more often see 〜こと.

What is で doing after 読むこと in 漫画を読むことで、毎晩少しずつ読んでいます。?

Here, で is the te‑form of だ/です (i.e., 〜で from 〜です), used to connect two clauses:

Think of the “full” version:

娘の一番の趣味は漫画を読むことです。そして、毎晩少しずつ読んでいます。
“My daughter’s favorite hobby is reading manga. And she reads a little every night.”

You can connect those two sentences more smoothly by putting です into its connective form で:

娘の一番の趣味は漫画を読むことで、毎晩少しずつ読んでいます。

So functionally, …読むことで、… ≈ “(it) is reading manga, and …”

This で is not “by/through” in the sense of 〜することで (= by doing ~) here; it’s best understood as the linking て‑form of です.

Why is 読んでいます used instead of 読みます at the end?

In Japanese, 〜ている has two main uses:

Progressive: an action in progress
- 今、本を読んでいます。 – I’m reading a book now.
Habitual: something done regularly / as a habit
- 毎晩テレビを見ています。 – I watch TV every night.

Here, with 毎晩 (every night), it’s clearly the habitual meaning:

毎晩少しずつ読んでいます。 – She reads a little bit every night (as an ongoing habit).

You could say 読みます, but 読んでいます emphasizes the ongoing, repeated nature of the activity more naturally.

What exactly does 毎晩少しずつ mean? How is it different from 毎晩少し?

Breakdown:

毎晩 – every night
少し – a little
ずつ – each / apiece / little by little

So 毎晩少しずつ means:

“a little each night”
with a nuance of bit by bit / gradually over time

Differences:

毎晩少し読んでいます。 – I read a little every night.
(Neutral “a small amount each night”, no special nuance.)
毎晩少しずつ読んでいます。 – I read a little bit each night, gradually.
(Suggests continuing slowly through a book/series.)

So ずつ highlights the idea of distribution over time: each time, a bit.

Who is the subject of 読んでいます? Why isn’t it stated?

The subject is still 娘 (my daughter).

Japanese often omits subjects when they are clear from context. The topic was introduced at the beginning:

娘の一番の趣味は… – As for my daughter’s number‑one hobby, …

After that, the speaker doesn’t need to repeat 娘は; it’s understood that we’re still talking about her:

（娘は）毎晩少しずつ読んでいます。 – (She) reads a little bit every night.

Omitting repeated subjects is very common and natural in Japanese.

Can the word order be changed? For example, can I say
娘の一番の趣味は、毎晩少しずつ漫画を読むことです。?

Yes, that’s perfectly natural, and actually quite common:

娘の一番の趣味は、毎晩少しずつ漫画を読むことです。
“My daughter’s number-one hobby is reading manga a little bit every night.”

In this version:

The hobby is described more fully as 毎晩少しずつ漫画を読むこと.
It’s a single X は Y です sentence, without using で to connect two clauses.

Both versions are fine:

娘の一番の趣味は漫画を読むことで、毎晩少しずつ読んでいます。
– Her hobby is reading manga, and she (in fact) reads a bit every night.
娘の一番の趣味は、毎晩少しずつ漫画を読むことです。
– Her hobby is “reading manga a little bit every night.”

The first states the hobby, then gives an example of her habit;
the second builds the habit into the definition of the hobby itself.