That looks cool! I like the consistent design ... and really need to learn to use free space the way you do.
Have you done the shop via couch too? And the slider ... is a repeatable region, or cloned pages, please?
If I may two small things, tho:
# I would place the hamburger to the right, at leat on mobile - it is more easily accessible with a thumb (but call it my preference, I gather that design usually requires compromises).
# With the books, have a look at "grid-template-columns: repeat(auto-fit, minmax(500px, 1fr));" - it may save you some tinkering with media queries (but then again, I need to look at some advanced stuff too).