I wanted to mention that DS has really enjoyed some William Sleator books lately. The Lexile scores are not terrifically high, generally in the 700s to 800s with a few higher or lower, but they seem to be well-constructed stories and he loves them. Ones he's liked:

The Green Futures of Tycho
Interstellar Pig
Singularity
House of Stairs

Anyone else discover these?

Striving to increase my rate of flow, and fight forum gloopiness. sick