Learn Polish: Czytam dalej tę książkę. - I am reading on with this book.

In Polish, adding the adverb dalej to an imperfective (ongoing action) verb is the standard way to say you are continuing to do something. So, czytam dalej means "I keep reading" or "I am continuing to read."

Why is the word for "this" spelled tę instead of tą here?

The phrase ta książka (this book) is the direct object of the verb czytam, so it must be in the accusative case. The correct accusative form of the feminine word ta is tę. Learners often confuse this with tą, which is the instrumental case form. While you might hear native speakers say tą książkę in very casual speech, tę książkę is the grammatically correct written form.

Could I use the perfective verb przeczytam instead of czytam here?

No, you must use the imperfective verb czytam. The word dalej describes an ongoing, unfinished process of continuing an action. Perfective verbs focus on the final result or completion of an action, so they cannot be paired with a word that means "to continue doing".

Is it okay to change the word order and say Dalej czytam tę książkę?