Adult
If you liked: Annihilation by Jeff Vandermeer you might like: Our Wives Under the Sea by Julia Armfield this comparison is going off vibes more so than story, but bare with me here. Both novels gave me the same feeling of subverbal psychological dread, that comes as much from the liminal/alien feeling enviroment as from within. They capture a feeling of paranoia and distrust for an enviroment that should feel safe, but now seems foreign.
If you liked: The Fall of the House of Usher by Edgar Allan Poe you might like: What Moves the Dead by T. Kingfisher A modern retelling that adds length, depth of character, and Kingfishers wonderful brand of humour to the already fantastic classic shortstory.
If you liked: Mexican Gothic by Silvia Moreno Garcia you might like: The Ghostwoods by C.J. Cooke building off the previous recommendation: if you liked the dilapidated, moldy-stained manorhalls of the House of Usher as a setting, both these novels borrow the atmosphere and put a whole new spin on "fungal horror"...
If you liked: It by Stephen King you might like: Black Mouth by Ronald Malfi A group of friends return to their hometown to confront a nightmare they first stumbled upon as teenagers.
If you liked: The Luminous Dead by Caitlyn Starling you might like: Dead Silence by S.A. Barnes Claustrophobic sci-fi horror about a lone female protagonist encountering a "haunting" in an alien-space setting.
If you liked: The Lost Village by Camilla Sten you might like: Ice Cold by Tess Gerritsen An eerie abandoned, snow-covered hides secrets and threads for our protagonists to uncover when they're snowed in by accident.
If you liked: Stephen King's 80's work you might like: The Book of Accidents by Chuck Wendig Chilling eighties-set horror, combining the terrors of real-life childhood trauma with a fantastical elements.
If you liked: Who Goes There - John Campbell you might like: All the White Spaces by Ally Wilkes A crew of men is haunted by an entity whilst stuck in the snowy landscapes of the arctic.
If you liked: The Willows by Algernon Black you might like: The Hollow Places by T. Kingfisher gothic-inspired horror set in a disorienting and hostile landscape of willow-trees. Any more info would be spoilers, but the vibes were so similar to me!
If you liked: The Fall of the House of Usher you might like: What Moves the Dead by T. Kingfisher A modern day retelling of the classic, about a house in decline, in more ways than one.
If you liked: The Shadow over Innsmouth by H.P. Lovecraft you might like: Deeplight by Frances Hardinge Eldridge horrors from the deepsea warp the minds of the inhabitants of a small fishermans-town in these gothic horror stories.
If you liked: The Haunting of Hill House by Shirley Jackson you might like: In the Night Wood by Dale Bailey or: House of Glass by Susan Fletcher gothic hauntings set in remote English manors, where the ghost could be supernatural or psychological in nature.
If you liked: Mouthful of Birds by Samanta Schweblin you might like: From the Neck Up by Aliya Whiteley short stories that explores our the horrors (large and small) of our modern day by warping the ordinary and mundane into the uncanny.
If you liked: House of Hollow - Krystal Sutherland you might like: The Watchers - A.M. Shine modern horror novels with a unique and terrifying take on the Irish changeling mythology.
If you liked Follow Me to Ground by Sue Rainsford you might like: Leech by Hiron Ennes Two speculative horror novels featuring unconventional healers that apply their Frankensteinean craft to mend, but search for answers in the bodies under their hands at the same time.
Young Adult
If you liked: Sawkill Girls by Claire LeGrande you might like:Wilder Girls by Rory Power Feminist YA horror featuring F-F romance.
If you liked: Wilder Girls by Rory Power, you might like: Horrid by Katrina Leno Combining body horror, grief and a whole lot of strangeness, both of these books are sure to unsettle and creep you out. It doesn't hurt that both are stunning to look at either.
If you liked: Sawkill Girls by Claire LeGrande you might like: The Dead and the Dark by Courtney Gould Small town horror featuring girls bonding together towards an evil force. Includes a diverse cast and F-F-romance in both.
If you liked: Here there are Monsters by Amelinda Bérube you might like: The Twisted Ones by T. Kingfisher This one only works one way for me personally, as I didn't love the former. If, like me, you liked the creepy forest setting and the idea behind these creatures, but didn't like the juvenile protagonists and teen drama: The Twisted Ones is for you. It also happens to be funny as an added bonus as well.
Middle Grade
If you liked: Ghostlight by Kenneth Oppel you might like: The Curse on Spectacle Key Brave young protagonists undertake a ghostly adventure investigating haunted lighthouses.
If you liked: Goosebumps by R.L. Stine you might like: Small Spaces by Katherine Arden what Goosebumps did for 80's and 90's kids, Katerine Arden is doing for kids of today. These series of books take a middle-grade spin on classic horror-tropes, destined to become classics themselves in the process.
If you liked: Ghost Girl by Ally Malinenko you might like: Spirit Hunters by Ellen Oh Our young protagonists are forced to form an impromptu and unlikely ghost-hunting gang to protect their friends, and find more friendship and bravery along the way
