"Have you ever wanted to speak like a Targaryen, command dragons like Khaleesi, or pray like a Red Priestess? Now you can learn High Valyrian as if you too were tutored like Tyrion. Valyrian is the ancient language of Essos from the universe of A Song of Ice and Fire. The full language and this course were constructed by linguist David J. Peterson. Spoken by educated Westerosi, and regarded as the language of nobles, poetry and dragons, High Valyrian is coming to Duolingo." — Duolingo Website
Over 80,000 people have started learning High Valyrian on Duolingo. High Valyrian is a conlang (fake language) used in the popular book and tv series Game of Thrones, otherwise known as A Song of Fire and Ice. It uses the same alphabets as the english language with some variations on their pronunciation and voicing. I've started learning it too. It's been fun to watch the newest episode of the series, while trying to follow along with some of the characters.
The sentence structure is a bit odd. It generally goes [subject - object - verb]. There are also no articles or verbs for the common "to be" like in english or many other languages. Nouns are also categorized as lunar, solar, terrestrial, or aquatic. Unlike many other languages on Duolingo that start with words like mother, father, eat, hello, and thank you, High Valyrian starts with words like sweat, swordsman, and knight. (This is probably common with conlangs on the site. I assume Klingon is the same.)