Martian Time-Slip by Philip K Dick - PKD is always pretty weird, but I found this one especially so. Time travel experiments by unlikable characters that involves abusing schizophrenic and autistic children.

Ancillary Justice by Anne Leckie - First of the Imperial Radch series. Told from the perspective of an intelligence that’s truly different than ours (even though it is ostensibly human). It made a lot of waves for having genderless characters, but that only scratches the surface of how strangely the narrator relates to the humans they’re dealing with.

Annihilation by Jeff VanderMeer - First of the Southern Reach series. A group of 4 unnamed individuals go to investigate a reality distorting phenomenon and reality gets heavily distorted. This one declares right up front that it’s going to get strange and does exactly that.