Learn Hardcore Esperanto: Ĉu vi jam legas la novan libron en la biblioteko? - Are you already reading the new book in the library?

It doesn’t translate directly into English as a standalone word, but it roughly corresponds to the “Do/Does/Is/Are/Have/Has” that we put at the start of English yes/no questions.
You put Ĉu at the very beginning of a yes/no question:
- Ĉu vi jam legas la novan libron en la biblioteko? – Are you already reading the new book in the library?
- Ĉu li venos morgaŭ? – Will he come tomorrow?

Unlike English, Esperanto does not invert subject and verb to make a question. You usually keep normal word order and just add Ĉu at the front.

Why is legas used here for “are reading”? Where is the progressive form?

Esperanto has only one present tense, formed with -as (here: legas), and it covers both:

simple present: you read
present progressive: you are reading

So:

vi legas can mean you read or you are reading, depending on context.
In this sentence, context and the word jam (already) make it clear that the meaning is Are you already reading…?

If you really want to emphasize ongoing action (like English progressive), you can say:

Ĉu vi jam estas leganta la novan libron…?

But this is usually unnecessary; Ĉu vi jam legas…? is the normal, natural form.

What does jam mean, and what does it add to the sentence?

Jam means “already”.

In this sentence:

Ĉu vi jam legas la novan libron en la biblioteko?
= Are you *already reading the new book in the library?*

It suggests that:

The speaker expected the reading to start at some point, and is checking if that has already happened.

Common contrasts:

jam = already
ankoraŭ = still / yet
ankoraŭ ne = not yet

Examples:

Ĉu vi jam manĝis? – Have you already eaten?
Mi ankoraŭ ne manĝis. – I haven’t eaten yet.

Why do novan and libron both end in -n?

The -n marks the accusative case in Esperanto (the direct object of a verb).

libro – a book (subject form)
libron – a book (object form)

Because nova libro (a new book) is the thing being read, it is the direct object of legas, so both words must show the accusative:

la nova libro – incorrect
la novan libron – correct

In Esperanto, adjectives agree with the nouns they describe:

same number (singular/plural)
same case (nominative/accusative)

So:

nova libro – a new book (subject)
novaj libroj – new books (subject)
novan libron – a new book (object)
novajn librojn – new books (object)

Why is it la novan libron and not just novan libron?

La is the definite article, like “the” in English.

la libro – the book
libro – a book (or just book in a generic sense)

In this sentence:

la novan libron implies a specific new book that both speaker and listener know about:
- maybe one that was just purchased,
- or one recently added to the library,
- or one already mentioned in the conversation.

If you said novan libron (without la), it would mean “a new book” in a non-specific way, which would not match the usual English meaning the new book in the library.

Why doesn’t en la biblioteko get an -n ending?

The -n ending is used for:

direct objects of verbs, and
some special uses (e.g. showing direction: en la domon – into the house)

But en la biblioteko here just shows location (where something is), not a direct object or direction. Location with prepositions like en (in), sur (on), sub (under) does not use -n when it’s just static position.

So:

en la biblioteko – in the library (location, no motion)
en la bibliotekon – into the library (motion toward it)

In this sentence we mean in the library, so:

en la biblioteko is correct,
en la bibliotekon would wrongly suggest movement into the library.

Does en la biblioteko mean the book is in the library, or that I am in the library reading it?

By itself, en la biblioteko can be ambiguous:

the new book that is in the library
reading (it) while in the library

Exactly the same ambiguity exists in English:
Are you already reading the new book in the library?

Context usually clarifies which is meant:

If you were just talking about a book the library bought, it likely means:
- the new book that is in the library.
If you were talking about someone going to the library to study, it may mean:
- reading it while in the library.

To be clearer in Esperanto, you could rephrase:

To focus on where the book is:
- Ĉu vi jam legas la novan libron, kiu estas en la biblioteko?
To focus on where you are reading:
- Ĉu vi jam legas la novan libron, dum vi estas en la biblioteko?
- Ĉu vi jam legas la novan libron ĉe la biblioteko? (less common, more “at the library”)

Could I say de la biblioteko instead of en la biblioteko?

Yes, but it changes the meaning:

en la biblioteko – in the library (location)
de la biblioteko – of/from the library

So:

Ĉu vi jam legas la novan libron en la biblioteko?
– Are you already reading the new book in the library?
Ĉu vi jam legas la novan libron de la biblioteko?
– Are you already reading the new book from the library / of the library?
(suggesting it is a library-owned or borrowed book, not necessarily that you are physically there)

Choose en if you want to stress place, de if you want to stress ownership/source.

Why is it Ĉu vi jam legas… and not something like Ĉu jam vi legas… or Ĉu vi legas jam…?

All three word orders are grammatically possible, but Ĉu vi jam legas… is the most neutral and natural.

Esperanto word order is relatively flexible, but:

Adverbs like jam usually appear just before the verb they modify, or before the whole verb phrase:
- Ĉu vi jam legas la novan libron…? – neutral, standard
- Ĉu vi legas jam la novan libron…? – possible, but less common
- Ĉu jam vi legas la novan libron…? – puts emphasis on “already you”, a bit stylistic

As a learner, you’re safest with:

Ĉu vi jam legas …

What is the difference between jam and nun here? Could I say Ĉu vi nun legas…?

Yes, you can say Ĉu vi nun legas la novan libron en la biblioteko?, but it changes the nuance:

jam = already – focuses on the fact that something has begun earlier than expected or requested.
nun = now – focuses on the time at this moment, without the “already” idea.

So:

Ĉu vi jam legas la novan libron…?
– Are you already reading the new book…?
(I expected you to start at some point; has that started yet?)
Ĉu vi nun legas la novan libron…?
– Are you now reading the new book…?
(I want to know what you’re doing right now.)

They are related in meaning but not interchangeable.

How would I answer this question in Esperanto, both “yes” and “no”?

Typical answers:

Jes, mi jam legas la novan libron en la biblioteko.
– Yes, I am already reading the new book in the library.
Ne, mi ankoraŭ ne legas la novan libron en la biblioteko.
– No, I am not yet reading the new book in the library.

You can also answer more briefly, if context is clear:

Jes, mi jam legas ĝin. – Yes, I’m already reading it.
Ne, ankoraŭ ne. – No, not yet.

Could I say Ĉu jam vi legis la novan libron…? with legis instead of legas? What’s the difference?

Yes, but legis is past tense (ending -is), while legas is present tense (ending -as).

Ĉu vi jam legas la novan libron…?
– Are you already reading the new book…? (ongoing action in the present)
Ĉu vi jam legis la novan libron…?
– Have you already read the new book…? / Did you already read the new book…? (completed action in the past)

So use:

legas if the reading is currently happening.
legis if you are asking whether the reading has been completed already.