Az ifjúsági könyv érdekes.

Hungarian has two forms of the definite article:

• a before a consonant sound
• az before a vowel sound

Here the next word is ifjúsági, which begins with the vowel i, so Hungarian uses az.

So:

• az ifjúsági könyv
• but a könyv

A useful thing to remember is that the article matches the next word it directly comes before, even if that word is an adjective modifying the noun.

Ifjúsági means youth, for young people, or sometimes young-adult / juvenile depending on context.

It comes from:

• ifjúság = youth
• -i = an adjective-forming ending meaning something like related to or belonging to

So ifjúsági könyv literally means something like youth-related book, but in natural English it is often best understood as:

• a youth book
• a book for young people
• a young adult book
  depending on context

Because the two adjectives are doing different jobs.

• ifjúsági is an attributive adjective: it directly describes the noun inside the noun phrase
  
  • az ifjúsági könyv = the youth book
• érdekes is a predicate adjective: it tells you something about the subject of the sentence
  
  • A könyv érdekes. = The book is interesting.

So in Hungarian:

• adjectives before the noun are usually part of the noun phrase
• adjectives after the noun are often the main statement about the noun

That is why the structure is:

• Az ifjúsági könyv = the youth book
• érdekes = is interesting

In Hungarian, the verb to be is often omitted in the third person singular and plural in the present tense.

So:

• A könyv érdekes. = The book is interesting.
• literally: The book interesting.

This is completely normal in Hungarian.

But the verb appears in other persons, for example:

• Érdekes vagyok. = I am interesting.
• Érdekes vagy. = You are interesting.
• Érdekesek vagyunk. = We are interesting.

So the missing is is not a mistake; it is just standard Hungarian grammar.

Hungarian adjectives usually do not agree with the noun in the way adjectives do in many Indo-European languages.

So:

• érdekes könyv = interesting book
• érdekes könyvek = interesting books

The adjective érdekes stays the same.

The noun carries the plural marking if needed:

• könyv = book
• könyvek = books

The same is true in predicate use:

• A könyv érdekes. = The book is interesting.
• A könyvek érdekesek. = The books are interesting.

Notice that in predicate position, plural adjectives often do take the plural ending -ek/-ak/-ok:

• singular: érdekes
• plural predicate: érdekesek

But in an attributive phrase before a noun, the adjective itself usually does not change:

• érdekes könyvek

Yes, it can be.

Ifjúsági könyv is a normal and common combination meaning a book intended for young people. In real usage, it can refer to:

• children’s/teen literature
• juvenile literature
• young adult literature

The exact English translation depends on context, but the Hungarian phrase itself is perfectly natural.

It can look intimidating, but it becomes easier when you break it up:

• if-jú-sá-gi

A few helpful points:

• stress in Hungarian is always on the first syllable
• ú and á are long vowels
• gy is a single consonant sound in Hungarian

So the main stress is on if.

A rough English-friendly guide might be:

• IF-yoo-shaa-ghee

That is only approximate, but it may help at first.

Könyv means book.

Two things often stand out to English speakers:

• ö is a front rounded vowel, somewhat like German ö or French eu
• ny is a single consonant, like ny in Spanish señor or roughly the ny sound in canyon

So könyv is approximately:

• kurnyv or kuhnyv
  but neither is perfect

The word ends in a difficult consonant cluster for English speakers, so learners often need practice saying it smoothly.

Yes, Hungarian word order is more flexible than English word order, but changing it usually changes the focus or emphasis.

The neutral sentence is:

• Az ifjúsági könyv érdekes.
  = The youth book is interesting.

You could also say:

• Érdekes az ifjúsági könyv.

This still means roughly the same thing, but it gives more emphasis to interesting, as if answering a question like What is the youth book like?

So the original version is the most neutral and straightforward.

Normally, no.

Ifjúsági does not usually mean possession here. It means related to youth or for young people, not belonging to the youth.

If you wanted to say the young people’s book, Hungarian would usually use a possessive structure instead.

So az ifjúsági könyv is understood as:

• the youth book
• the book for young people
• the YA book

not usually the young people’s book.

The sentence breaks down like this:

• Az = the
• ifjúsági könyv = youth book / book for young people
• érdekes = interesting

So the grammar is:

• [definite article + noun phrase] + [predicate adjective]

In other words:

• subject: Az ifjúsági könyv
• predicate: érdekes

This is a very common and useful Hungarian sentence pattern.