Learn Dutch: Vergeet je het boekje? - Are you forgetting the little book?

In Dutch, to turn a statement like Je vergeet het boekje (You are forgetting the little book) into a yes/no question, you swap the subject and the verb. This puts the verb at the beginning: Vergeet je het boekje?

The translation says 'Are you forgetting', but there is no 'are' or '-ing' word in the Dutch sentence. Why?

Dutch generally doesn't use a separate 'am/is/are + -ing' form for things happening right now. The simple present tense verb vergeet can mean both 'forget' and 'are forgetting'.

What does the -je at the end of boekje do?

Adding -je to a noun makes it a diminutive, meaning 'small' or 'little'. So boek (book) becomes boekje (little book). A helpful rule to remember is that all diminutive words take the article het.

If I want to ask 'Are you NOT forgetting the little book?', where would niet go?

You would place it at the very end: Vergeet je het boekje niet? When negating the specific action in a sentence like this, niet gets pushed to the end.