For the vast majority of your pages, your perspective looks really extreme, and while that's okay for some of them, it was advised that you err more on the side of having more boxes with shallower foreshortening. You seemed to have realized this by about the last ten or so pages, and then your main problem seemed to be getting your edge on the usually-invisible side of the cube to align with the other three lines of that axis, which is incredibly common and expected.

I know how hard this challenge can be, so I don't want to tell you to go back and redo it, but I would've liked it if you had done shallower boxes throughout. As long as you think you can draw shallow boxes well, I'll go ahead and mark you as complete and see what other people say. Then you can move on to Lesson 2.