A mezőgazdasági szakkönyv részletes.

In Hungarian, the verb to be is usually left out in the present tense when the sentence is in the third person singular or plural.

So:

• A mezőgazdasági szakkönyv részletes. = The agricultural textbook is detailed.

There is no separate word for is here, even though English requires it.

Compare:

• Én fáradt vagyok. = I am tired.
• Te fáradt vagy. = You are tired.
• Ő fáradt. = He/she is tired.

So in your sentence, részletes is the predicate, and Hungarian simply does not need van here.

A is the definite article, meaning the.

So:

• a / az = the

Hungarian has two forms:

• a before most consonant sounds
• az before vowel sounds

Here, the next word is mezőgazdasági, which starts with m, so Hungarian uses a:

• a mezőgazdasági szakkönyv = the agricultural textbook

Yes. Mezőgazdasági means agricultural.

It comes from:

• mezőgazdaság = agriculture
• mezőgazdasági = agricultural

The ending -i is very common in Hungarian for making an adjective meaning related to or connected with something.

For example:

• gazdaság = economy
• gazdasági = economic
• mezőgazdaság = agriculture
• mezőgazdasági = agricultural

So mezőgazdasági szakkönyv literally means something like agriculture-related specialist book, i.e. agricultural textbook / professional book on agriculture.

Szakkönyv is a compound noun:

• szak = field, specialty, profession, subject area
• könyv = book

Together, szakkönyv means a specialist book, professional book, technical book, or sometimes textbook/reference book, depending on context.

So:

• mezőgazdasági szakkönyv = agricultural specialist book / agricultural textbook

It is a single word because Hungarian very often forms compounds this way.

Mezőgazdasági directly describes the noun szakkönyv, so it is an attributive adjective:

• a mezőgazdasági szakkönyv = the agricultural textbook

But részletes comes after the noun phrase and functions as the predicate adjective:

• részletes = detailed
• A mezőgazdasági szakkönyv részletes. = The agricultural textbook is detailed.

So:

• mezőgazdasági = adjective inside the noun phrase
• részletes = adjective saying something about the whole subject

This is similar to English:

• the agricultural textbook
• the textbook is detailed

No. In this sentence, részletes stays the same.

Hungarian adjectives do not usually agree with the noun in the way adjectives do in many European languages. There is no masculine/feminine/neuter agreement, and no singular/plural agreement here.

So:

• a könyv részletes = the book is detailed
• a könyvek részletesek = the books are detailed

Notice that in the plural predicate form, részletes becomes részletesek, because it is standing as the predicate for a plural subject. But inside a noun phrase, adjectives usually stay unchanged:

• részletes könyv = detailed book
• részletes könyvek = detailed books

So in your sentence, részletes is singular because szakkönyv is singular.

The neutral word order here is very natural:

• A mezőgazdasági szakkönyv részletes.

This is a straightforward topic + comment structure:

• A mezőgazdasági szakkönyv = what we are talking about
• részletes = what we say about it

Hungarian word order is flexible, but changes often affect emphasis rather than basic meaning.

For example, this sentence is the normal, unmarked version. If you moved things around, it would usually create special emphasis or sound less neutral.

So for a learner, this sentence is best understood as a standard pattern:

• [subject] + [predicate adjective]

A rough English-friendly guide is:

• meh-zuh-goz-daa-shee-ghee

A few important points:

• ő is a long front rounded vowel, somewhat like the vowel in French peu or German schön, but longer.
• á is a long vowel, like a broad aa sound.
• sz is pronounced like English s
• s by itself is pronounced like English sh
• g is always a hard g, as in go

So in mezőgazdasági:

• sz sounds like s
• the s in -sági sounds like sh

That is why the end sounds roughly like -shaa-ghee.

A rough guide is:

• sok-koenyv or sak-kernyv, depending on how close you want to get

Important pronunciation points:

• sz = English s
• kk is a long/doubled consonant, so hold it slightly longer
• ö is like German ö or French eu
• ny is like the ny in Spanish señor, or similar to n+y blended together
• v is pronounced normally

So szakkönyv is approximately:

• sak-könyv

with a clearly doubled k and a soft ny sound.

It is neutral and perfectly normal, though the vocabulary is somewhat formal/academic because of the noun mezőgazdasági szakkönyv.

The grammar itself is very ordinary:

• definite article
• noun with adjective
• predicate adjective
• no present-tense is

This is exactly the kind of sentence structure Hungarian uses all the time.

Grammatically, yes, but it means something different.

• A mezőgazdasági szakkönyv részletes. = The agricultural textbook is detailed.

But:

• A szakkönyv mezőgazdasági. = The specialist book is agricultural.

In that second sentence, mezőgazdasági becomes the predicate adjective, so now you are saying what kind of specialist book it is.

So the position matters:

• before the noun: adjective inside the noun phrase
• after the noun phrase: predicate adjective

That is a very important distinction in Hungarian.