This is nice! Since you mentioned you wanted to be mobile first, I should mention a couple issues I ran into on my phone:
The header bar, with Login and Signup on the right, did not fit on my screen (stopped right around the "S" of Signup), and I was not able to horizontal scroll the header to get to that link, even though it look like it would be horizontal scrollable.
It seemed like while I was interacting with the book on the front page, either the book jumped up and down or the vertical scroll jumped up and down (I'm not sure which) as the sell-text was written and removed.
Thanks for this feedback! Really appreciated - I'm working on an overhaul of the landing page but I'm going to quickly fix these two issues in the mean time.
The header bar, with Login and Signup on the right, did not fit on my screen (stopped right around the "S" of Signup), and I was not able to horizontal scroll the header to get to that link, even though it look like it would be horizontal scrollable.
It seemed like while I was interacting with the book on the front page, either the book jumped up and down or the vertical scroll jumped up and down (I'm not sure which) as the sell-text was written and removed.