A Thousand-Page Novel–Made Up of Mostly One Sentence – Captures How We Think Now (nytimes.com)

The Gates of Paradise by Jerzy Andrzejewski was published in 1960. It consists of 40,000 words in two sentences. The second sentence is "And they marched all night" [1].

[1] https://en.wikipedia.org/wiki/The_Gates_of_Paradise