Dung,
That is truly a matter of personal preference. When I studied for the PMP Exam, I tried the Rita book and I didn't like it. It simply didn't work for me. (That much said, I want to make it clear that thousands of people have used it and passed the exam because of it. It just didn't "jive" with me. That's all).
So if you are happy with the book from Phillips and if you feel that you are well prepared then don't buy another book. Instead, I recommend that you spend that money on an online PMP Exam simulator and practice on exam questions instead. I recommend
www.pm-prepcast.com/readysetpass