Ja czytam książkę o jedzeniu.

I am reading a book about food.

Breakdown of Ja czytam książkę o jedzeniu.

• ja: I
• czytać: to read
• książka: the book
• o: about
• jedzenie: the food

Questions & Answers about Ja czytam książkę o jedzeniu.

Why is Ja used at the beginning of the sentence? Is it mandatory?

Ja means I and is the first-person singular pronoun. In Polish you usually drop it because the verb ending already shows the subject. It’s included here for emphasis or clarity. You’d hear more naturally:
Czytam książkę o jedzeniu.

What is czytam and how is it formed?

Czytam is the first-person singular present tense form of the verb czytać (to read). The base infinitive is czytać, and you remove -ąć and add the present ending -am for “I”:
czytać → czyt + am = czytam

Why is książkę in that form and not książka?

Because książka (book) is feminine and it’s the direct object of the verb. Polish uses the accusative case for direct objects. The accusative singular of feminine nouns ending in -a changes to -ę, so książka becomes książkę.

What does the preposition o require, and why is jedzeniu used?

The preposition o (about) in Polish requires the locative case. Jedzenie (food) is a neuter noun. In the locative singular, neuter -e nouns gain -u, giving jedzeniu.

Could I rearrange the word order here?

Yes, Polish word order is flexible. The most common neutral order is S-V-O: Ja czytam książkę o jedzeniu or dropping the pronoun: Czytam książkę o jedzeniu. You could also say O jedzeniu czytam książkę for a slight topicalization of o jedzeniu.

Is there another way to say “about food” more formally?

Yes. Instead of o jedzeniu, you could use the phrase na temat jedzenia (literally “on the topic of food”). It’s a bit more formal:
Czytam książkę na temat jedzenia.

How do you pronounce these words?

An approximate guide:
czytam – CHIH-tam (ż~zh sound + i=j short, a as in “car”)
książkę – ksh-YONGK-eh (ą nasal ~ “ong”, ś=ksh, ę ~ “eh” nasal)
o jedzeniu – oh yed-ZHEH-nyu (j=y, dzhe as in “j” in “jam”, iu ~ “yu”)

Why isn’t the infinitive used, like “Ja czytać książkę o jedzeniu”?

In Polish you use a conjugated verb for the person doing the action. An infinitive like czytać is non-conjugated and would need another verb (e.g., chcę czytać – I want to read). You need czytam for “I am reading.”