One question... why the sentence "I eat an apple" is translated as "Ich essen einEN Apfel" but this one "I write a book" it is "Ich schreibe ein Buch" instead of EINEN Buch?
Isn't it the same case in both sentences? And if not.. which is the difference?
EDIT: (Auto-solved my own doubt, sorry ^^. I thought Buch was masculine but it was Neuter so that explains it)
I write a book; I am writing a book; I do write a book. These are all present tense, though each one in English can have different connotations.
"I am writing a book" is the present progressive tense, indicating that something is taking a while to do. This would be the translation most used in English, but the one given is not wrong.
German would use ich schreibe ein Buch for all three of the above English translations.