Alasdair Gray’s 1981 debut novel Lanark: A Life in Four Books is a standalone dystopian surrealist work. Or to look at it another way, it’s one part straightforward literary fiction and one part portal fantasy (of sorts).
Lanark is an unsocial man living in the troubled city of Unthank. Duncan Thaw is a socially deficient inhabitant of Glasgow. The two men are connected in ways of which neither is immediately aware. And why would they be aware? They inhabit different realities.