Just my $.02 as a user who came to your site: The landing page is still unfortunately very confusing - what I wanted to do most is to just try it out really quickly to see how it looked.
But, it took me a while (after I had scrolled through to the bottom of the site) to understand that I had to click the start learning. Then, thre was the sign-up modal that showed up on the other page; From how it came up, it felt to me like I had no option but to sign-up, and I would've turned away at that point. BUT, because I had read a couple of your posts, I knew it was possible. So I tried clicking outside of it and then it worked. Then, I picked a language and then I had this list of items which were not clear to me what they were, exactly (from the blogs I knew this was the library). So, I clicked on one.
And then it was beautiful. Like, no joke, the actual reading experience was... perfect. It worked... flawlessly.
Your core product is very, very good! It is definitely your strongest asset. Don't hide it behind the splash page, then sign-up-modal-you-have-to-dismiss, then the library UI... get users to experience your core product as quickly as possible... that'll get 'em hooked!!!