Learn Hardcore Polish: Wieczorem zaczynam czytać nową książkę. - In the evening I start reading a new book.

Wieczorem is the instrumental singular of wieczór (evening), used adverbially to mean in the evening. Polish often uses bare case forms (especially instrumental) for time expressions: wieczorem (in the evening), nocą (at night), latem (in summer), zimą (in winter). No preposition is needed here because the form itself carries the “in the …” meaning.

Can I say w wieczór to mean “in the evening”?

Not in modern Polish. The natural way is wieczorem. If you need to be more specific, say dzisiaj wieczorem (this evening/tonight) or combine with a day: w poniedziałek wieczorem (on Monday evening).

Why does the sentence start with Wieczorem? Is the word order flexible?

Yes, Polish word order is flexible. Fronting time/place is common to set the scene. Variants like these are all fine, with slight shifts in emphasis:

Wieczorem zaczynam czytać nową książkę.
Zaczynam czytać nową książkę wieczorem.
Nową książkę zaczynam czytać wieczorem. (emphasizes the object)

Is zaczynam present or future? Why does it sound like “I’m starting tonight”?

Grammatically it’s present tense (1st person singular of zaczynać), but Polish often uses the present of imperfective verbs for scheduled or near-future plans. With wieczorem, it naturally means “I’m starting this evening.”

What’s the difference between zaczynam and zacznę here?

Wieczorem zaczynam czytać… = I’m starting this evening (plan/schedule, very natural in speech).
Wieczorem zacznę czytać… = I will start this evening (explicit future, a bit more definite). Past reference would be: Wczoraj zacząłem/zaczęłam czytać… (I started yesterday; masculine/feminine speaker).

Why is it czytać and not przeczytać after zaczynam?

After verbs like zaczynać/zacząć (to begin), you normally use an imperfective infinitive to denote an ongoing activity: zaczynam czytać. Perfective przeczytać means “to read (and finish),” so zaczynam przeczytać is ungrammatical. To express intention to finish, you might say: Zamierzam przeczytać tę książkę (I intend to read it through).

Why nową książkę and not nowa książka?

Because czytać takes a direct object in the accusative case. Feminine nominative is nowa książka, but feminine accusative is nową książkę (both adjective and noun change).

Do adjectives have to agree with nouns?

Yes, in gender, number, and case. Examples with książka (feminine):

Nominative: nowa książka
Accusative: nową książkę
Genitive: nowej książki The adjective nowy/nowa/nowe changes to match the noun.

Where are the English articles “a/the”? How do I say them in Polish?

Polish has no articles. nową książkę typically corresponds to English “a new book.” If you mean “the new book,” use context or a determiner:

tę nową książkę = this/the new book (specific)
jakąś nową książkę = some new book (unspecified)

Do I need to say ja?

No. The verb ending in zaczynam already shows 1st person singular. You can add Ja for emphasis or contrast: Ja wieczorem zaczynam…

How do I negate this sentence?

Put nie before the verb, and note that a negated direct object usually switches to genitive:

Wieczorem nie zaczynam czytać nowej książki. (I’m not starting to read a new book this evening.) If you negate reading in general:
Wieczorem nie czytam książek.

How do I say this as a habitual statement (in the evenings)?

Use wieczorami (in the evenings, habitually). For a routine activity:

Wieczorami czytam.
Wieczorami zaczynam czytać około dziewiątej. Saying Wieczorami zaczynam czytać nową książkę sounds odd because you don’t normally start a new book every evening.

Any pronunciation tips for this sentence?

Stress is always on the second-to-last syllable in Polish.
Wieczorem ≈ vye-CHO-rehm (cz = ch in “church”).
zaczynam ≈ za-CHI-nam (cz = ch; y = the hard i in “roses”).
czytać ≈ CHY-tach (czy = chih; ć = soft “ch”).
nową ≈ NO-vown (ą is a nasal vowel, like French “on”).
książkę ≈ kshonzh-keh (ksi ≈ kshi; ą ≈ on; ż = zh; final ę often sounds like plain “e”). Don’t over-nasalize final ę; many speakers pronounce it almost like e.

Are there other ways to say “in the evening”?

Yes:

dzisiaj wieczorem or dziś wieczorem = this evening/tonight (explicit)
tego wieczoru = that evening (narrative/past context)
pod wieczór = toward evening, late in the day
wieczorami = in the evenings (habitually)

Can I say Zaczynam nową książkę like English “I’m starting a new book”?

It’s understandable but can be ambiguous (starting to write? starting to read?). It’s more natural to specify:

Zaczynam czytać nową książkę. (starting to read)
Zaczynam pisać nową książkę. (starting to write)

What’s the difference between zaczynać and zaczynać się?

zaczynać is transitive: you begin something. Example: Zaczynam czytać książkę.
zaczynać się is intransitive: something begins. Example: Film zaczyna się wieczorem. (The movie starts in the evening.)

Could I use a more formal synonym for zaczynać?

Yes, rozpoczynać/rozpocząć is a more formal synonym:

Wieczorem rozpocznę czytanie nowej książki. Note that with rozpocząć, using the verbal noun (czytanie) is common in formal style.

How would I make the subject plural or change the object to plural?

Subject plural: Wieczorem zaczynamy czytać nową książkę. (We start…)
Object plural: Wieczorem zaczynam czytać nowe książki. (accusative plural: nowe książki)

How do I say “this evening/tonight I will start reading a new book” explicitly?

Use an explicit time adverb and the perfective future:

Dziś wieczorem zacznę czytać nową książkę. This leaves no ambiguity about the time or the futurity.

Can I move wieczorem to the end?

Yes: Zaczynam czytać nową książkę wieczorem. It’s natural and fully correct; the emphasis is a bit more on the action than on the time.