I love the idea, but I’m having a very hard time with legibility with the extra bold serif font.

It’d be nice to have the ability to select a few different fonts. Georgia, Tisa, and Merriweather are considered very legible serif fonts.

Sans-serif is generally considered easier to read on a digital screen — Helvetica, Open Sans, Roboto, PT Sans, and Verdana are very good options.

It looks like you’re using Literata — but you’re relying on the font-weight property to generate the bold weight. These aren’t “true” weights, the browser artificially creates it. Also, not all browsers render “font-weight” equally, so for maximum legibility it’s best to use the exact weight of the original font.

It’s like oblique v italic. Oblique will give you the slant, but it’s not a real italic. Font designer’s consider many different variables when crafting italic and bold styles, the aren’t just slanted or relying on additional stroke for the heavier weights.

Lastly, I think it would be helpful if the font size was bigger. Because you’re focusing on each letter / word, after awhile it starts blurring together.

But overall it’s a fantastic concept, and you have a great selection of titles as well. Very cool.

EDIT: Regarding fonts, the most legible ones are the ones that have equal character weight. You'll notice with Literata the bars "horizontal line in e, A, f, t, etc" are very thin while the stems & shoulders are quite thick. A famous example of this concept pushed to the extreme is the font Didot, which is featured on the cover of Vogue magazine.

These make for beautiful heading fonts, but poor paragraph fonts as the wide variety in width reduces overall legibility. You probably noticed this with Literata at its regular font weight which is why you changed the font-weight to bold, but I would consider selecting a different font altogether.