I have added two readings for this week (one more than I wrote about last week). The Field chapter, as I said before, is accessible and good. The Singer article is a classic. Though SAS-heavy, the article basically "launched" mixed effects in the behavioral sciences, and so I have drawn heavily on her step-by-step examples for our class.
For next week, I now specified the Singer reference (left undefined in the syllabus) as Chapters 3 & 4 from her recent book with Willett. Again, these chapters are _as_ accessible as this literature gets.
I'm suggesting that all the other readings I have made available this week and next (HOX, LUKE, KREFT) might be things you file away for advanced future reference...but I don't think you should spend much time on them now