。
Could you book a room for me?
Literal
Room [object-を] book [could you do for me?-てくれませんか]?
Uses ~てくれませんか, a polite request form that literally asks 'won't you do X for me?' The benefactive くれる frames the action as a favor to the speaker. 部屋を取る here means 'to book/reserve a room.'