Books are one of favorite family collections. I really love adding books that are not only fun but that we can all learn from (hence the different holiday ones we have and love!). We put away all of our seasonal and holiday books in a plastic container and when we pull them out it's like they are all brand new! But don't feel like you have to buy a bunch at once, I add a couple every year ( our collection started 7 years ago for Zoe's first Christmas).
A Very German Christmas ( my brother and his little family live in Switzerland and I love the idea of the girls learning these stories)