I don't recommend a manual for P, but a good textbook, as the material with P you should really learn very well, since you will see it come up in every preliminary exam afterward. (Exam C, for example, assumes that you essentially remember everything from P, no joke.)
As to what I recommend, I suggest Probability and Statistics with Applications: A Problem-Solving Text.
This is all purely anecdotal, so I'm certainly not bashing anyone with praise for Actex. I can't find the exact manual I bought, but it looked exactly like this with an orange cover. I bought it at the beginning of 2014.
I barely even opened it while studying. I had taken a probability course right before really studying for P, so this could be why. But, in my experience, it was much quicker and convenient to use Google/Wikipedia for any questions I had. They were very reliable, too.
This is where I got a lot of progress done. I took a peek, and it looks like his exams and video solutions are all still free. I would highly recommend taking these exams and watching the video solutions. I felt like I learned a lot about both the content and formatting of the exam.
Best of luck!