I have to say that one of my favorite text choices were the verticle text sets. I think about the multi-level adult education classes and having a selection of easy to difficult readings about the same subject would serve all students as well as encourage some more complex reading.
I agree! Vertical and horizontal text sets were my biggest take-aways from Chapter 5. "Text + 1 (2,3,4) More" was an even simpler way to think about it. It might be interesting to let members of a multi-level group self-select the level of text that they want to read, and then monitor whether their selections' accessibility are as they predicted.