Just finished reading through all four weeks. It is laid out clearly with awesome assignments that have the student working deeply with the story yet not tediously. Characters, plot, setting, theme are all covered. Several writing and non-writing assignment options are given depending catering to different learning styles. I feel it would definitely be strong enough for a high school level as long as you requred the assignments to be done on the more complex side of the scale.
I “bit” and got it, too, and I agree, if you require longer essays regularly instead of just paragraphs, it would be high school material, if you really follow through and do the discussing and require the essays. We may end up doing some of this, some of Lightning Lit at times. I think you WOULD need to have had previous essay form instruction, also.