What's the Name of That Book??? discussion

This is an adult fantasy/surrealist fiction book about an estrange son and mother(?). The son is confined to a mental facility, has tried to escape a few times. He has written a seemingly nonsensical kids fantasy story/book while in the mental facility and now the story seems to be coming alive and attacking the heroes (there are others, a writer, a boy and girl?. i honestly don't remember details.

I do remember a setting in an old cabin in the woods by a stagnant pond. A monster that resembled a facehugger from aliens that could glide/fly?

I read the book 2 or 3 years ago, but it was definitely an older book, i'd imagine late 80s/early 90s.

I think it started with a Z or had some really obscure title. But that could be wrong, that' sjust what's sticking in my head. thanks

Do you recall anything about the cover? Was it a long book, short book? Anything about where the book was set (e.g. 1980s US, 1960s England, near-future Canada)?

hardcover. white with abstract designs/figures if I remember correctly. of average size maybe 9x5 or so. not too thick. only a could hundred pages or so

Zod Wallop by William Browning Spencer looks likely?

Here's the cover of one edition that sounds like your description:

yes! definitely this! thank you all!