Learn Hardcore Croatian: Sadržaj ovog romana je jednostavan, ali emocije su duboke. - The content of this novel is simple, but the emotions are deep.

ovaj roman = this novel (nominative case, used for the subject)
ovog romana = of this novel (genitive case, used to show possession or belonging)

The phrase sadržaj ovog romana literally means the content of this novel.
Because English can say the content of this novel or this novel’s content, you see of in English, but Croatian shows that relationship with the genitive case instead of a separate preposition.

So:

Sadržaj ovog romana je jednostavan = The content of this novel is simple.
If you said Ovaj roman je jednostavan, that would mean This novel is simple, a different sentence.

What is the grammatical role of sadržaj in this sentence?

Sadržaj (content) is the subject of the sentence in the first clause:

Sadržaj ovog romana = The content of this novel (subject)
je = is (verb)
jednostavan = simple (predicate adjective describing the subject)

So the core structure is: Sadržaj … je jednostavan = The content … is simple.

Grammatically:

sadržaj is masculine singular, nominative (subject form)
ovog romana is a genitive phrase modifying sadržaj (content of this novel)

Why is the adjective jednostavan and not jednostavno?

Jednostavan is the adjective form agreeing with a masculine singular noun (sadržaj).

sadržaj = masculine singular
therefore the basic nominative masculine singular form of the adjective is jednostavan

Jednostavno (ending in -o) is usually:

the neuter singular adjective form (e.g. rješenje je jednostavno – the solution is simple), or
an adverb, meaning simply (e.g. On jednostavno ne razumije – He simply doesn’t understand).

Here we are describing the noun sadržaj, which is masculine, so we need jednostavan, not jednostavno.

Why do we have je in the first part but su in the second part (je jednostavan, ali emocije su duboke)

Both je and su are forms of the verb biti (to be), and they must agree with the subject:

Sadržaj … je jednostavan
- subject: sadržaj (singular)
- verb: je (3rd person singular of biti)
emocije su duboke
- subject: emocije (plural)
- verb: su (3rd person plural of biti)

So:

singular subject → je
plural subject → su

That’s why we don’t repeat je in the second clause; we change it to su to match emocije.

Why is there a comma before ali? Is that required in Croatian?

Yes, in standard Croatian a comma is normally used before the conjunction ali (but) when it connects two clauses:

Sadržaj ovog romana je jednostavan, ali emocije su duboke.

This is similar to English when you link two full clauses:

The content is simple, but the emotions are deep.

So in Croatian:

[clause 1] , ali [clause 2]
The comma is normal and expected in writing.

Why is emocije plural? Could we use singular emocija?

Emocije is the plural of emocija (emotion), and Croatian very often talks about feelings in the plural, just like English does:

emocije = emotions, feelings (plural)
emocija = an emotion (singular)

In this sentence, emocije su duboke suggests a range or collection of feelings involved in the novel, not just a single emotion. English uses plural here too: the emotions are deep.

You could construct a sentence about a single emotion (e.g. Emocija je duboka – The emotion is deep), but that would be a different idea and would sound unusual in this literary context.

Why does duboke end in -e? What is it agreeing with?

Duboke is the adjective dubok (deep) in the feminine plural nominative form, agreeing with emocije:

emocije = feminine plural, nominative (subject)
duboke = feminine plural nominative of dubok

Adjectives in Croatian must agree with the noun in:

gender (masculine / feminine / neuter)
number (singular / plural)
case (nominative / genitive / etc.)

So:

dubok sadržaj (masc. sing.)
duboka emocija (fem. sing.)
duboke emocije (fem. plural)

Here, emocije su duboke = the emotions are deep.

Why is there no word for the in Sadržaj ovog romana?

Croatian does not have articles (a/an/the) like English.

Specificity is usually expressed by:

context
demonstratives like ovaj (this), taj (that), onaj (that over there)
possessives (moj, tvoj, etc.)

In this sentence:

Sadržaj ovog romana is understood as The content of this novel, even though there is no explicit word for the.
ovog already makes it specific: of this novel.

So:

roman can mean a novel / the novel, depending on context.
ovaj roman clearly means this novel (and therefore also kind of functions like this specific novel).

Could the word order be Emocije su duboke, ali sadržaj ovog romana je jednostavan?

Yes, grammatically that word order is fine:

Emocije su duboke, ali sadržaj ovog romana je jednostavan.

Croatian word order is relatively flexible. Changing the order often changes:

what is emphasized
what is taken as given information vs new information

Original:

Sadržaj ovog romana je jednostavan, ali emocije su duboke.
Emphasis: the content is simple, but the emotions (unexpectedly) are deep.

Reversed:

Emocije su duboke, ali sadržaj ovog romana je jednostavan.
Emphasis: the emotions are deep, but the content (surprisingly) is simple.

Both are correct; they just highlight different aspects.

Can je or su be omitted in this kind of sentence?

In standard written Croatian, in sentences like this you normally keep je and su:

Sadržaj ovog romana je jednostavan.
Emocije su duboke.

In everyday spoken Croatian, people sometimes drop je (and less often su) in certain contexts, especially in short statements or when the verb is easily understood from context. For example in speech you might hear something like:

Sadržaj ovog romana jednostavan, ali emocije duboke.

However:

This is more colloquial.
For learners and for correct writing, it’s better to always include je / su in such sentences.

What is the difference between ovog and ovoga? Could we say sadržaj ovoga romana?

Ovog and ovoga are both genitive singular masculine forms of ovaj (this).

ovog romana
ovoga romana

Both are grammatically correct and mean of this novel.

Difference:

ovog is the short form – more common in everyday speech and writing.
ovoga is the full form – can sound more formal, emphatic, or stylistically marked, and is frequent in careful or poetic language.

In your sentence, Sadržaj ovog romana je jednostavan is the most neutral, natural version, but Sadržaj ovoga romana je jednostavan is also correct.

Could we say Radnja ovog romana je jednostavna instead of Sadržaj ovog romana je jednostavan?

Yes, but it changes the nuance slightly.

sadržaj = content (all the material in the book: plot, themes, ideas, etc.)
radnja = plot, storyline (what actually happens in the story)

So:

Sadržaj ovog romana je jednostavan = The overall content is simple (broadly).
Radnja ovog romana je jednostavna = The plot/storyline is simple.

Note the agreement change:

radnja is feminine singular → jednostavna (fem. sing.)
sadržaj is masculine singular → jednostavan (masc. sing.)

Both sentences are correct; choose the noun that matches what you want to say.

Is ali the only way to say but here? What about no or međutim?

Croatian has several words that translate as but, with slightly different tones:

ali – the most common, neutral but
no – also means but, often a bit more formal or stylistic
međutim – however, usually starts a sentence or after a stronger pause

Possible variants:

Sadržaj ovog romana je jednostavan, ali emocije su duboke. (most neutral)
Sadržaj ovog romana je jednostavan, no emocije su duboke. (a bit more literary/formal)
Sadržaj ovog romana je jednostavan. Međutim, emocije su duboke. (two sentences; however)

All are grammatical; ali is the most typical choice in this simple structure.