The love scene in question:
At this, Eliza and Ezra rolled together into one giggling snowball of full-figured copulation, screaming and shouting as they playfully bit and pulled at each other in a dangerous and clamorous rollercoaster coil of sexually violent rotation with Eliza’s breasts barrel-rolled across Ezra’s howling mouth and the pained frenzy of his bulbous salutation extenuating his excitement as it whacked and smacked its way into every muscle of Eliza’s body except for the otherwise central zone.
More review snippets here. One includes the line, “do not read this book.” https://en.wikipedia.org/wiki/List_of_the_Lost#Reception
One can imagine him struggling to imagine the scene well enough to write it, then going to a toy shop, buying a Barbie and a Ken and spending the next half hour mashing them against each other in an attempt to visualise it.