To dobry wybór dla czytelnika.

In Polish, the present-tense verb jest is often omitted in sentences like this, especially with to.

So:

• To dobry wybór dla czytelnika. = natural and common
• To jest dobry wybór dla czytelnika. = also correct, just more explicit

Both mean the same thing.

Because dobry has to agree with wybór.

The noun wybór is:

• masculine
• singular
• nominative

So the adjective also takes the masculine singular nominative form: dobry.

Compare:

• dobry wybór = a good choice
• dobra książka = a good book
• dobre rozwiązanie = a good solution

That is a very common question. In this kind of to sentence, Polish normally uses the nominative form:

• To dobry wybór.

So wybór stays in the nominative.

Learners often expect wyborem because Polish sometimes uses the instrumental after być, for example:

• On jest nauczycielem. = He is a teacher.

But with to in a sentence like this, dobry wybór is the normal form.

Because dla means for, and dla requires the genitive case.

The dictionary form is czytelnik = reader.
After dla, it changes to czytelnika.

So:

• czytelnik = reader
• dla czytelnika = for a reader / for the reader

It can mean either one. Polish has no articles, so there is no direct equivalent of English a or the.

That means dla czytelnika could mean:

• for a reader
• for the reader
• sometimes even a more general for readers

The exact meaning depends on context.

Literally, czytelnik is a masculine noun, so it refers to a male reader. In some contexts, Polish uses masculine forms generically, especially in more general statements.

If you want to say for a female reader, you would use:

• dla czytelniczki

So this sentence may refer to a male reader specifically, or it may be using a general masculine form depending on context.

Yes. Polish word order is more flexible than English word order.

The most neutral version is:

• To dobry wybór dla czytelnika.

But you could also say:

• Dla czytelnika to dobry wybór.

That puts more emphasis on for the reader. The meaning stays very similar, but the focus changes.

Polish stress is usually on the penultimate syllable.

So:

• wybór → wy-BÓR
• czytelnika → czy-tel-NI-ka

A few sound notes:

• cz sounds roughly like English ch in chocolate
• ó is pronounced like u
• y is a Polish vowel with no exact English equivalent

So czytelnika may take some practice, especially the beginning czy-.

Yes, very normal. It is the standard way to say a good choice.

Polish usually places descriptive adjectives before the noun, just like English in this case:

• dobry wybór = good choice
• ciekawa książka = interesting book
• trudne pytanie = difficult question

So this part of the sentence is very straightforward and natural.