Ta powieść ma piękną okładkę, ale jej tytuł jest bardzo smutny.

Ta means this for a feminine singular noun in the nominative case.

Powieść is feminine, so Polish uses:

• ten for masculine
• ta for feminine
• to for neuter

So:

• ta powieść = this novel

If the noun changed case, the form of ta could change too.

In Polish, many feminine nouns do end in -a, but not all of them. Some feminine nouns end in a soft consonant, and powieść is one of them.

So you simply have to learn powieść as a feminine noun. You can also see that it is feminine because other words agree with it:

• ta powieść
• the possessive idea in jej tytuł refers back to that feminine noun

This is a common pattern with nouns ending in -ść.

Because they are in the accusative case.

The verb ma means has, and the thing that someone or something has is the direct object, which in Polish usually takes the accusative.

Dictionary forms:

• piękna = beautiful
• okładka = cover

Accusative forms:

• piękną
• okładkę

So:

• ma piękną okładkę = has a beautiful cover

For many feminine nouns and adjectives ending in -a, the accusative singular changes like this:

• -a → -ę for the noun
• -a → -ą for the adjective

Yes — jej can mean either her or its, depending on context.

Here it means its, because it refers back to powieść (novel), which is a feminine noun in Polish.

So:

• jej tytuł = its title

Even though English usually uses its for things, Polish uses the same word jej for:

• her
• its when the thing referred to is a feminine noun

Because jej agrees with the owner of the title, not with the noun tytuł.

The title belongs to the novel, and powieść is feminine, so you get jej.

Also, jej is a possessive form that does not change here to match the gender of tytuł. So you say:

• jej tytuł = its title
• jej okładka = its cover

Even though tytuł is masculine and okładka is feminine, jej stays the same.

Because smutny describes tytuł, not powieść.

In the second clause, the subject is:

• jej tytuł = its title

And tytuł is a masculine noun, so the adjective must also be masculine:

• tytuł jest smutny = the title is sad

If the adjective described powieść, then it would be feminine:

• powieść jest smutna = the novel is sad

Tytuł is in the nominative case.

That is because it is the subject of the verb jest in the second clause:

• jej tytuł jest bardzo smutny

So the structure is:

• tytuł = subject
• jest = is
• bardzo smutny = very sad

This contrasts with okładkę, which is accusative because it is the direct object of ma.

Yes, absolutely.

That would also be natural, and it means:

• This novel has a very sad title

The original sentence says:

• This novel has a beautiful cover, but its title is very sad

So the second half uses is instead of has:

• jej tytuł jest bardzo smutny

Both patterns are normal in Polish:

• ma smutny tytuł = has a sad title
• tytuł jest smutny = the title is sad

The version in your sentence creates a nice contrast between:

• ma piękną okładkę
• jej tytuł jest bardzo smutny

Because in Polish, ale (but) is normally preceded by a comma when it joins two parts of a sentence.

So:

• Ta powieść ma piękną okładkę, ale jej tytuł jest bardzo smutny.

This is standard Polish punctuation. English also often uses a comma before but in similar sentences, so this usually feels familiar to English speakers.

Bardzo means very.

It intensifies the adjective:

• smutny = sad
• bardzo smutny = very sad

It does not change for gender, number, or case. It just stays bardzo.

This word order is the most neutral and natural one:

• Ta powieść ma piękną okładkę, ale jej tytuł jest bardzo smutny.

Polish word order is more flexible than English, so other versions are possible for emphasis, for example:

• Ta powieść ma piękną okładkę, ale tytuł jest bardzo smutny.
• Ta powieść ma piękną okładkę, ale bardzo smutny jest jej tytuł.

But the original sentence is the clearest and most standard for a learner.

A few words here can be hard for English speakers:

• powieść: roughly po-vyeshch
• piękną: roughly pyengk-non (the nasal vowel is approximate here)
• okładkę: roughly o-kwat-keh
• tytuł: roughly ti-too-uw
• smutny: roughly smoot-nih

A few helpful notes:

• w sounds like English v
• ł sounds like English w
• ś is a soft sh-like sound
• ę is a nasal vowel, and its exact pronunciation can vary a bit depending on position

These are only rough English approximations, but they can help you get started.