You can say: "わたしのほんはどこですか" (Watashi no hon wa doko desu ka) Or you can replace watashi for watakushi (わたくし). Please note that Watakushi is pronounced like: Watakshi. You don't have to emphasize the ku. Watakushi is basically a more formal and polite way to say I. If you're talking to someone who is more superior to you, I'd recommend you say watakushi! ^^ Men can say: ぼくのほんはどこですか (Boku no hon wa doko desu ka). This is more informal. Women can say: あたしのほんはどこですか (Atashi no hon wa doko desu ka). This is also more informal. You don't need 'O' in front of 'hon', but good guess! You can read a little about 'o' on this site: http://japanese.about.com/library/blqow20.htm 'Dochira' is kind of like 'what direction' or 'where', but you don't use it for your own things. 'Dochira' is polite and it is used in regards toward someone else like what kahokoji said.

the most simple way to say that is '(watashi no) hon wa doko desu ka' 'dochira' is more like 'which'. and I'm not sure but I think that if you want to add polite preffix to 'book' you use 'go' not 'o', so it should be 'gohon'. but I'm not sure about it, I think the easiest way is just to say 'hon'.

' watashi no hon wa doko desu ka' is correct. 'O-hon' is strange, usually japanese don't put polite prefix like 'O-' to book. 'dochira' is sometimes used as 'where' as a polite words to other persons belongings, but in this case, you ask about your belongings so the suitable one is 'doko'.