First, it is NOT "The Color Out of Space" I'm looking for, but it takes its influence from Lovecraftian themes. I remember reading it in an anthology containing Lovecraft-inspired horror (similar to Black Wings of Cthulhu).
The basic premise is that a science team finds an asteroid and decides to land to study it. After setting up camp, they find that the asteroid keeps changing in size, the flow of time shifts constantly, and something in the asteroid is driving them to madness.
One of the main things I remember that happens in the story is that, as the science team tries to return to their ship to escape, they keep running into ghostly reflections of themselves in the past/future going in different directions, meaning that their escape is futile because of the changing shape of the asteroid.
I read this anthology about a year or so ago, at a Barnes and Noble (United States). I know I got it off the shelf, but I don't remember if it was a new release, or something that had been out for a while. Don't remember anything about the cover of the anthology.
Some other details I remembered about the story:
It was told as a series of journal/log entries by different members of the science team, pretty much telling of how they landed on/in the asteroid, exploring it, and how they were starting to lose their minds to this eldritch, unknown thing inside.
The science team were using mulebots, or something similar: basically robotic beasts of burden to carry equipment as well as explore further into the asteroid. There's a mention of one of these mulebots becoming stuck in a passage where earlier it had been wide enough to go through, which starts off the suspicion that the asteroid is changing size/form around them.
I think (and I'm not sure on this) the story ended with just the pilot and one of the main scientists alive, having made it back to their ship, but not able to find the way out of the asteroid that they came in. So they fly deeper into the asteroid and then... something happens? It's Lovecraftian in nature; basically they die but not really because they just keep flying endlessly into the asteroid.