This IS an interesting discussion. I tend to agree with Derrick at this point that there is nothing new under the sun. By that, I don't mean that we can't be inspired to create something exciting, vibrant and alive. And it certainly doesn't mean that we should be copying other people's work or ideas verbatim and passing them off as our own. But, to me, there is definitely a difference between being ripping something off and being inspired by it. I think research is key to executing a book idea or concept! I look at other designs/products/colors etc before and after I am working on a project. I've found that both ways are helpful to my process. As designers, we see and then we create. You can't help but look all around you and soak up whatever might inspire you and whatever might help you, especially when generating good ideas and concepts!
As far as my inspiration, I love to browse through Anthropologie. It is my favorite place to just stroll through. I always feel happier the minute I walk through the doors. When I see designs, ads, books, really any piece that I like, I pull it out or put it aside so I can place it in my little box in which I put things that inspire me. Then I go back and make books of those things so that I can look through at any point for inspiration. Sadly, I have not had occasion to keep up with this lately, but it is something I love to do and it helps me stay inspired.