A young writer with an addiction to drugs attempts to write his masterpiece on a serial killer. Hopeless, he finds himself in a world of bizarre delusion and questions his reality.

My poor attempt:

While researching material for his book about a serial killer, a disaffected writer spirals deeper into his drug addiction until delusional fantasy blurs with reality.

I'm picturing an American Psycho-type character study. Could be intriguing...

Good luck with it,
Monique

I like the premise, but it seems to wordy to me.
"with an addiction to drugs" just plain "drug addict" would suit better for a logline.

Keep playing with it, I think your close.
best of luck.