I do like this bookcase and the way you do it. It is not a criticism of any kind, just a consideration; From the pictures I can’t figure out for sure the proportions of the cross on the sides of the bookcase. Maybe this element would look still better if the horizontal beam were the same width as the vertical.
This looks really nice, so nice that I’m not sure if it is still the prototype. If it’s the prototype, one choice is whether you reverse the rails and stiles on the top. The choice is whether you want to see the haunch from the front, as you have it now, or if you want a continuous front edge, and see the haunch from the side. Having it on the front separates the two haunches, while having them closer together on the narrower side might make them stand out more and affect how you see the side. I can’t decide which I prefer…Maybe, as you have it now.