Timelessness

I'm co-leading the girls' book club at the library this summer. I realized today that we are reading an equal number of newer books (Rodzina, The Green Glass Sea) and old favorites that have been around since my childhood. (Tuck Everlasting, From The Mixed-Up Files of Mrs. Basil E. Frankweiler.)

All of these books take place in the past. The only one that had a contemporary setting when it was written was The Mixed Up Files, but looking at 1960's prices (27 cents for a hot fudge sundae!) and icons (the Automat) makes it historical today. Yet it doesn't feel dated.

That got me thinking about timelessness in books. Why do some books remain favorites while others fade into dated-ness? I was a big Bobbsey Twins fan as a kid. Those books were old fashioned even then. I reread a few of them recently and realized just how dated they are. And I challenge you to find a kid under twelve who has heard of them. My sister read Sweet Valley High. Those were so popular they had a television show. I don't think I've ever seen one check in or out at the library.

What do you think makes a book timeless? Do you strive for that in your work, or is it something that never occurred to you?