Questions & Answers about Ég vil kaupa bókina sem er á borðinu.
Because bókina is the form needed for a direct object.
- bókin = the book in the nominative case, usually used for the subject
- bókina = the book in the accusative case, used here because it is the thing being bought
In this sentence, ég is the subject and bókina is the object of kaupa.
In Icelandic, the definite article is usually added to the end of the noun instead of being a separate word.
So:
- bók = book
- bókin = the book
- bókina = the book in the accusative
This is one of the first big differences English speakers notice, since English uses a separate word the.