Looking for a SciFi book

[MammonAzrael]

A friend is looking for books like A Wrinkle in Time to teach to their students, and so I am turning to the Playground for your expertise.

Any suggestions are welcome, but the books have to meet a few requirements:

It must be SciFi, not Fantasy.
It must be roughly 6th grade reading level.
It must be no longer than roughly 200 pages.
It must deal with abstract concepts (light/dark, good/evil).

So, any ideas? Our frontrunner for a while was Hitchhiker's Guide, but the reading level was just a little too high. What are your ideas? Thanks!

[BWR]

What exactly do you mean by 'light/darkness' as an abstract concept? Do you have any agendum? I.e. do you have a specific conclusion you wish to come to?
Do you accept merely thinking about slightly odd concepts as 'abstract', like most of the best SF does? You know, trying to communicate with aliens with radically different mindsets, etc.
Because you can probably find a lot of good stuff by various Golden Age authors. The one that did it for me was Arthur C. Clarke, in a short story collection called "Of time and stars", but Bradbury's "The Martian Chronicles" might also be a good choice..

Do you want books that are equally preachy as L'Engle and try to sell you a certain religion?
If so, look no further than C.S. Lewis. "Perelandra", the second book of his Space trilogy (the other two are not really necessary to read and understand P.)
And I don't really see how HHGttG would be on your list; it's a lot longer than 200 pages, it's not really about abstract concepts other than as a source of jokes, and perfectly readable at 6th grade level (at least I found it so, but I will confess to being quite a bit better at reading than most of my classmates - I don't know if I was so much better that it would matter in this case).

A slightly out-there suggestion Star Wars: Shatterpoint by Matthew Stover. It's quite dark, probably the darkest SW book ever written. It's bascially Heart of Darkness in SW, but it's easily read and delves into the problems of terrorists/freedom fighters, the demhumanizing effect war has on all parties and how in the end no one really wins. It has the bonus that the main character is Mace Windu, which should hopefully make it a tad more accessible and interesting to kids.

[Kitten Champion]

How about The Giver by Lois Lowry? It deals in abstract concepts and I enjoyed it in the 6th grade. They're also making it a feature film, so... there's that.

The Colors of Space by Marion Zimmer Bradley was one of the books I read in grade school and still enjoy. It's a good introductory text to SF about not seeing the world in clear black and white terms, humanizing the alien in a fairly direct metaphor.

[J-H]

Can "Abstract" include "scientific concepts that most 12 year olds won't have thought of?"

If so, look to the works of Hal Clement. Close to Critical, Mission of Gravity, Iceworld, etc.

Of the Heinlein juveniles, Tunnel in the Sky and Space Cadet both come to mind.

[CarpeGuitarrem]

Darn, that's a tall order. Suggesting something on the par of L'Engle?

[lightningcat]

I also read the Giver in middle school. Solid recommendation.