Learn Dutch: Ik heb een boek gekregen.

It is the past participle of the irregular verb krijgen (to get / to receive). Because it is irregular, it doesn't follow the standard rules for making a past participle. It takes the common ge- prefix and -en ending, but the vowel in the middle changes from ij to e.

Why does the Dutch sentence use heb (have) if the English translation is just "I got"?

Literally, this sentence means "I have received a book." In everyday spoken Dutch, this structure (using "have" or "be" plus a past participle) is the most natural and common way to talk about things that happened in the past, even where English prefers the simple past tense like "got".

Why is gekregen placed at the very end of the sentence?

This is a classic rule of Dutch word order. When a sentence has a helper verb (like heb) and a past participle (like gekregen), the helper verb takes the second spot in the sentence, and the past participle gets pushed all the way to the end. This creates a "sandwich" around the other words in the sentence, which in this case is een boek.

Can I use gekregen for any time I want to say "got" in English?

No, you have to be a bit careful here! The English word "to get" has many different meanings, such as "to fetch" or "to become". The Dutch verb krijgen (and its past participle gekregen) specifically means "to receive" or "to be given" something.