Hollow Knight [official site] was a Kickstarter project I remember being captivated by because of the art style. It’s all bluey greys and underground exploration to solve a mystery – kinda elegiac. There’s a beta awaiting further exploration in my Steam library but I’ve only been able to dip in for small chunks of time thanks to a set of trips and other distractions. HOWEVER that didn’t stop me emailing the game devs about the artwork. As a result artistic lead, Ari Gibson, has opened his sketchbooks (at one point literally) for RPS.
Here is a whole bouquet of concept art along with Ari’s own comments and explanation.
N.B. Clicking the sketchbook images takes you to a slightly larger version but otherwise what you’ll see when you click through is the same picture, but it turns them into a clickable slideshow which can be a nicer way to look at concept art as it greys out the rest of the page and lets you concentrate :)