syuumatu ni hon wo yomu zikan wo huyasimasu.

に marks a specific time when something happens, so 週末に means on the weekend or at the weekend.

In this sentence, 週末に tells you when the speaker will increase their reading time.

A few examples:

• 週末に勉強します。 = I study on the weekend.
• 夜に本を読みます。 = I read books at night.

Yes, sometimes.

• 週末に focuses on the time expression itself: on the weekend
• 週末は makes the weekend the topic: as for the weekend...
• 週末 without a particle is also sometimes used in casual Japanese

For example:

• 週末に本を読む時間を増やします。 = I will increase the time I spend reading on the weekend.
• 週末は本を読む時間を増やします。 = As for the weekend, I will increase the time I spend reading.
• 週末、本を読む時間を増やします。 = A natural casual version

So に is very normal here, but not the only possibility.

In Japanese, a verb phrase can directly modify a noun that comes after it.

So:

• 本を読む = to read books
• 時間 = time

Together, 本を読む時間 means the time for reading books or more naturally the time I spend reading books.

This is one of the most important Japanese patterns:

• 日本に住む人 = a person who lives in Japan
• 昨日買った本 = the book I bought yesterday
• 本を読む時間 = time to read books / time spent reading books

Because 読む is a verb modifying 時間, not a noun modifying a noun.

Use の mainly when one noun modifies another noun:

• 日本の学校 = Japan’s school / a school in Japan
• 私の本 = my book

But when a verb modifies a noun, Japanese does not use の:

• 本を読む時間 = time to read books
• not 本を読むの時間

If you use の, the structure changes:

• 本を読むの can mean the act of reading books But that is a different grammar pattern.

Each を belongs to a different verb relationship.

1. 本を読む

   • 本 is the direct object of 読む
   • You read a book / books

2. 時間を増やします

   • 時間 is the direct object of 増やします
   • You increase time

So the sentence contains a smaller phrase inside a bigger one:

• 本を読む = read books
• 本を読む時間を増やします = increase the time spent reading books

This is completely normal in Japanese.

増やします is the polite form of 増やす, which means to increase something.

It is a transitive verb, so it takes an object:

• 時間を増やす = increase time
• 数を増やす = increase the number
• 予算を増やす = increase the budget

A useful comparison:

• 増える = to increase, to go up, to become more
  
  • 時間が増える = the amount of time increases
• 増やす = to increase something
  
  • 時間を増やす = increase the amount of time

In your sentence, the speaker is actively increasing the time, so 増やします is the right choice.

Japanese non-past forms often cover both present and future.

So 増やします can mean:

• I increase
• I will increase

In this sentence, it usually sounds future-oriented or like a planned habit change:

• I will increase the time I spend reading on weekends
• or I increase the time I spend reading on weekends in a habitual sense

The exact meaning depends on context.

It can mean either, depending on context.

Japanese nouns usually do not show singular vs. plural the way English does. So 本 could mean:

• a book
• books
• book reading in a general sense

In a sentence like this, English often translates it naturally as books or reading:

• the time I spend reading books
• the time I spend reading

Japanese leaves that number unspecified unless it really matters.

The basic structure here is very natural:

• 週末に = time
• 本を読む時間を = object phrase
• 増やします = verb

Japanese word order is more flexible than English, especially for time expressions. For example, these are also possible:

• 本を読む時間を週末に増やします。
• 週末に、本を読む時間を増やします。

But the verb usually comes at the end, and the original sentence is the clearest and most standard order.

Japanese often omits the subject when it is obvious from context.

So even though English usually needs I, we, or someone else, Japanese often leaves it out:

• 週末に本を読む時間を増やします。 = I will increase my reading time on weekends.
• It could also mean we or another understood subject if the context says so.

This is very common and natural in Japanese.

Normally, Japanese is written without spaces:

• 週末に本を読む時間を増やします。

The spaced version is usually just for learners, to make the parts easier to see:

• 週末 に 本 を 読む 時間 を 増やします。

So the spaces are a teaching aid, not standard Japanese writing.