Eu quero ler o capítulo final agora.

Yes, you often can leave eu out in Portuguese because the verb form quero already shows that the subject is I.

So:

• Eu quero ler o capítulo final agora.
• Quero ler o capítulo final agora.

Both are natural.

Including eu can add:

• emphasis
• clarity
• contrast

For example:

• Eu quero ler o capítulo final agora, mas ele quer esperar.
  I want to read the final chapter now, but he wants to wait.

Portuguese often uses two verbs together, just like English:

• quero = I want
• ler = to read

So quero ler literally means I want to read.

This is a very common pattern:

• quero comer = I want to eat
• quero dormir = I want to sleep
• quero sair = I want to go out

The first verb (querer) is conjugated, and the second verb stays in the infinitive form.

After querer (to want), the next verb normally stays in the infinitive.

So:

• quero ler = I want to read
• quero estudar = I want to study
• quero viajar = I want to travel

This works much like English want + to + verb, except Portuguese does not need a separate word equivalent to to before the second verb here.

O is the masculine singular definite article, meaning the.

• o capítulo = the chapter

Portuguese uses definite articles more often than English does. In this sentence, o capítulo final means the final chapter, referring to a specific chapter.

Because capítulo is masculine singular, the article must also be masculine singular:

• o capítulo
• o livro
• o problema

If the noun were feminine, you would use a:

• a página final = the final page

In Portuguese, adjectives usually come after the noun.

So:

• capítulo final = final chapter
• livro interessante = interesting book
• filme bom = good movie

This is one of the most common adjective patterns in Portuguese.

Some adjectives can come before the noun, but final in this meaning is very naturally placed after capítulo.

Yes, here final means last or final.

So o capítulo final means:

• the final chapter
• the last chapter

In this context, both are good translations.

Just remember that final is an adjective here, describing capítulo.

Yes, agora can move around, but the version in the sentence is very natural.

• Eu quero ler o capítulo final agora.
• Agora eu quero ler o capítulo final.
• Eu agora quero ler o capítulo final.
  (possible, but less common in everyday speech)

Putting agora at the end often sounds smooth and natural, especially when it gives a sense of right now.

Word order in Portuguese is somewhat flexible, but some positions sound more natural than others.

Capítulo has the stress on the syllable tí:

• ca-PÍ-tu-lo

The accent mark in capítulo shows where the stress goes.

Without getting too technical, the written accent helps you pronounce the word correctly. In Brazilian Portuguese, it sounds approximately like:

• kah-PEE-too-loo

That is only an approximation, but it helps English speakers notice that the stress is not on the first or last syllable.

In Brazilian Portuguese, ler is usually pronounced roughly like:

• lehr

The e is not exactly like English air or bed, but somewhere in that area depending on accent. The final r in Brazilian Portuguese is often softer or more breathy than an English r, especially at the end of a word.

So for learners, a rough guide is:

• ler ≈ lehr

Just remember that Portuguese r sounds can vary a lot across Brazil.

Usually, no—not if you mean the final chapter of a book.

• o capítulo final = the final chapter
• um capítulo final = a final chapter

Using um would sound less natural in this context, because a book normally has one specific final chapter, so Portuguese prefers the definite article o.

It is neutral and completely natural in both speech and writing.

Nothing in the sentence is especially formal or especially casual. You could say it in everyday conversation, and you could also write it.

If you wanted a more casual spoken version, you might simply drop eu:

• Quero ler o capítulo final agora.

Yes. Changing quero changes the attitude or intention.

For example:

• Eu preciso ler o capítulo final agora. = I need to read the final chapter now.
• Eu vou ler o capítulo final agora. = I’m going to read the final chapter now.
• Eu gostaria de ler o capítulo final agora. = I would like to read the final chapter now.
• Eu devo ler o capítulo final agora. = I should / must read the final chapter now.
  (depends on context)

So quero specifically expresses wanting.

Here is the breakdown:

• Eu — subject pronoun (I)
• quero — verb, 1st person singular of querer (want)
• ler — infinitive verb (to read)
• o — definite article (the)
• capítulo — noun (chapter)
• final — adjective (final / last)
• agora — adverb (now)

This structure is very common in Portuguese: subject + conjugated verb + infinitive + article + noun + adjective + adverb