It depends on the length of the trip. If it’s a short trip I usually just take whatever I am reading. Since I like to travel lightly the most books I will carry are three, current read plus two back-ups.
I don’t own an e-reader but have been debating about getting one for the longest time. I enjoy holding the book in my hands and flipping the pages, which is why I have been resisting. However, I am beginning to see the benefits of getting one. An e-reader would take up less space in my bag and I could carry more than one book without adding weight to my bag.