Learn Dutch: Begrijp jij het boek? - Do you understand the book?

In Dutch, you make a yes/no question by putting the verb in the very first position, swapping it with the subject. Instead of saying Jij begrijpt (You understand), you put the verb first to ask Begrijp jij...? (Do you understand...?). Notice that Dutch doesn't use a helper word like "do" for questions!

Wait, shouldn't the verb for jij have a "-t" at the end (begrijpt)?

Usually, yes! But there is a special spelling rule for questions: when the verb comes before jij or je (meaning "you" singular), you drop the -t at the end. So it is Jij begrijpt but Begrijp jij?.

Could I use je instead of jij in this sentence?

Yes, you can absolutely say Begrijp je het boek?. Jij is just the emphasized version of je. You use jij when you want to put specific focus on the person, like asking "Do you understand the book? (Because I certainly don't!)".

Why is it het boek and not de boek?

In Dutch, there are two words for "the": de and het. Boek happens to be a "het-word" (a neuter noun), so it always takes het. You just have to memorize which "the" word goes with a noun when you learn new vocabulary.