X-link to the DRM-free megathread, for new bundles with horror content in them:
Humble Audiobook Bundle Goosebumps presented by Scholastic features the popular Goosebumps series of kids/YA horror adventure novels by R. L. Stine, with 4 titles at the minimum level, 5+ more at the better-than-average, and 3 more at the top-tier.
The Video Game Bundle 7.0 from StoryBundle includes in its $12 top-tier both audiobook & e-book versions of the illustrated horror-ish adventure novel
MONA.