。
Please give me a book.
Literal
Book [object-を] give-[please-ください].
A simple polite request. 下さい is the polite form of くれる ('give to me'). With kanji 下 ('below'), the etymology implies 'give from above to below' (to the speaker). Commonly written in hiragana ください in modern usage. Subject (the giver) omitted.