There's also a free weekend on Steam for SUNLESS SEA, offering the chance to see how well you sail in the dark, gratis. Steam News has the announcement, while this post expands further with word on new content that's just been released for the game along with Steam trading cards and badges. Here's the plan:

New in Sunless Sea: The Rose-Market
Collectors and eccentrics gather on Roser's Wharf, eager to buy curiosities from returning zee-captains. Can you navigate the market's archaic customs and turn a profit?

The Rose-Market appears irregularly in London, and offers an unpredictable opportunity to earn a good price for many less-used items.

In addition, after your captain has some zeefaring experience, new options will open on ten islands, allowing you to explore some of the stranger customs of the unterzee and exchange lesser items for more valuable ones. The items you can earn are - coincidentally! - popular among Rose-Market collectors.

Steam trading cards and badges
By popular demand, Sunless Sea now has Steam trading cards and badges! Scholars of the Correspondence will be very interested to discover the badges, as each is a sigil with a corresponding definition. We look forward to seeing you all discover them together!