Why do you want to buy this book?
Kimi wa naze kono hon o kaitai no desu ka.
you; buddy; pal; monarch; ruler; sovereign; (one's) master
topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis
this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)
book; volume; script; this; present; main; head; real; regular; counter for long cylindrical things; counter for films, TV shows, etc.; counter for goals, home runs, etc.; counter for telephone calls
indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.
to buy; to purchase; to value; to have a high opinion; to stir; to provoke
indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question
indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way