When I first translated this sentence I wrote "you write the book". Then, I realized that in English the "proper" way to say it would be you "wrote" the book. But, after I got the answer wrong, I realized that I need to stop thinking of how it's said in English, rather, think how it's said in Italian...
Great point about considering how things are said in Italian! That's a big step in learning a language. But "proper" has little to do with the difference between "write" and "wrote". These are two different verb tenses. You write the book now, but you wrote the book yesterday :)
How is it bad? I am from Spain and the audio seems pretty legit to me. Please consider that vowels form a dipthongue when you find them in the end of a word and the beginning of the next one. In this case, we have "scrivi il". It is not pronounced "scri-vi-il" at a normal pace, but "scri-vil": TU-SCRI-VIL-LIBRO. Look for those clusters in the fast audio and things might start falling into place.
I keep getting mixed up with when I should use a definite article. e.g. sometimes it is there, as the l'acqua in 'tu bevi l'acqua' or in this sentence il libro. Then sometimes it is not used like in 'Io mangio zucchero'. Can someone explain why there is and sometimes isn't a definite article?
Sometimes there is a definite article because it is part of the practice. I write the book, and I write a book. There is a difference there between the two, just as there would be in Italian. Also generally things (nouns) like sugar or sand are in a class called 'uncountable' and so unless you are talking about some specific sugar or sand, you don't use an article. French does something similar with a few nouns. Ex. I like to eat sugar, I like to eat the sugar. I like to eat a sugar. Since sugar is an uncountable noun, you don't use A for sugar. I like to eat a sugar is usually wrong. (there are exceptions sometimes) I'd imagine that Italian is similar in this regards.