I will always recommend the Necrososcope series by Brian Lumley - vampires, werewolves, mind powers, and the protag talks to the dead - he makes friends with a dead scientist, learns an equation, and can use the mobius equation to open doorways to anywhere - the first couple of books are slow, but it is soo much fun to read!

Last Days by Brian Evenson has really stuck with me, one of the best and most creative in the ‘cultist’ subgenre. Also seconding Negative Space by BR Yeager.

A Head Full of Ghosts by Paul Tremblay, Things Have Gotten Worse Since We Last Spoke by Eric LaRocca, The Troop by Nick Cutter.

The Deep by Nick Cutter.

I’m not sure if it’s a case of hindsight, but I finished reading this right before the titanic sub incident and it definitely unlocked a new fear.

I’ve just finished The Ritual by Adam Neville and I’m never reading again