Some of the favorite stories of my childhood (e.g., C.S. Lewis's Narnia Chronicles, Lloyd Alexander's Prydain Chronicles, Madeleine L'Engle's Wrinkle in Time, and L.F. Baum's Oz series) seemed to gloss over details such as most basic life needs such as food gathering, eating, sleeping, clothing/grooming/bathing and waste elimination. I still enjoy re-reading these stories from time to time. Newer fantasy series like Harry Potter and more adult fantasy works such as Elizabeth Moon's Deed of Paksenarrion seem to have a lot more detail on the minutiae of day-to-day life. For example, in Deed of Paksenarrion, Elizabeth Moon talks about logistics such as having to dig out the "jacks", having to transport, forage and distribute food to troops, and the niceities (or not) of various sleeping arrangements. These details are generally not covered in J.R.R. Tolkien's Lord of the Rings trilogy. Both works succeeded in entertaining me, but they definitely had different feels to them.

In reviewing my NaNoWriMo'03 work Twilight, my older sister complained about scenes where the main character (a seven year old named Giovanna) spends time dealing with the lack of bathroom facilities or pre-packaged foods in her travels to other worlds. She cites Lewis's Narnia books as a prime example of how fantasy books do not need to delve into such mundane issues (though I recall even there scenes of wrapping up bear meat and later roasting it with apples--perhaps food related details are "ok"?).

How does an author decide what level of detail/realism is appropriate, especially for fantasy novels? Where should the focus of the story be? Can modern works written in styles popular in an earlier time succeed in the market place?

As an example, in Twilight, in some worlds, there aren't flushable toilets or bathrooms. This, to me, seems like a point I would need to address--in reading about the world, wouldn't the reader be curious about details like this? Don't details about how people gather and prepare food, how they bathe (especially in places where water is scarce), and where they sleep help define a new world to the reader? On the other hand, most details such as these are not present in Narnia and that series doesn't suffer for it. How can I reconcile these views?

Some other details for consideration/discussion:

• When my young character is traveling to different worlds and encountering different environments, peoples and cultures, it seemed natural to me that she have some concern in each place for how to handle: procurement of food (this is one of the things that varies from world-to-world and helps to illustrate the diversity of what she encounters); preparing and eating that food (it's one thing to gather nuts and berries; but what is "safe" to eat and how can a seven year old make it appetizing?); where to sleep (in one scene, she and the dog crawl beneath the branches of an evergreen tree for some shelter and end up huddling together for warmth; in another, she tries to fall asleep on a rough wooden floor in a tavern); and where to eliminate bodily waste (most of the worlds she visits do not have bathrooms). The last element isn't added for comic effect but simply to emphasize the changes that the main character must make to her life style in order to survive.
• In My side of the mountain (a great children's book by Jean Craighead George), Sam, the main character, has to make a life for himself in the wilderness. The author goes into a lot of detail about how he finds and prepares food, how he creates living quarters (in a hollowed out tree), and how he entertains himself. Bodily waste elimination doesn't get mentioned (perhaps there are different levels of taboo behavior).
• In Lavondyss (a modern fantasy work about a place where mythological archetypes (mythagoes) wander through a wood and interact with the human heroes), Robert Holdstock goes through great detail that sometimes leaves the reader feeling uncomfortable (such as a scene where a shaman wears the preserved human skin from another character). This work is clearly not intended for children and perhaps Holdstock employs the reader discomfort as a way of showing the strangeness of the realm he has created.

Does what gets included in stories simply depend upon the targeted age of the reader? What makes works such as Narnia and Lord of the Rings, which skip over many of these basic life details, so timelessly classic and effective?

Thanks for your advice/help.