Books??

I have been packing for my trip to Paris and Venice last night and by the time I came to choosing some books for the train-ride I faced a major problem.
Ok, I can only take pockets because they are small and light and cheap so it is not a disaster when they are lost during the voyage. But which ones to take? I have a huge pile in my library with books that I haven't read yet, and then there are the ones I love so much I can just read them over and over again. For the moment the only one who is definitely going to make it is Rowling's HP Half-Blood Prince.
Good thing the pocket came out just in time for the Holidays, I really need to re-read this one ASAP for the ...th time. But what else should I take??