hi xuhaifeng
As txdentist said you look very lost in this. Kaplan is a rather expensive and lenghty preparation course. Unless you have several months to prepare don't even bother on paying for the course. Actually if you're planning for next July, don't even bother on the book, since you're probably won't have enough time.
If you check some previous threads on this forum, you'll find all kind of advice.
I personally recomend dental decks and released tests, and go to the librabry often to use books as reference when you need some detailed information. This is because most question in the actual exam are recycled, so usually decks and released tests will do. Plus, the Kaplan book has waayyyy too many details in it, which may cause you to spend too much time on each subject.
In case you do have enough time to prepare, go ahead and buy the an USED Kaplan book, and use it together with the other material you can get. I said used, because you can only get it new directly from Kaplan when you join the course, which "ain't worth it".
Of course, all this depends on the level of preparation you got from the school you graduated from, and the time you have to study. You know different countries, different curriculum.
Well, good luck, sincerely 🙂
