The gist is simple: Poliphilo has a strange dream in which he searches for the woman he loves. But the way it's told is so complicated that even most Renaissance scholars -- the same people who read Plotinus while waiting for the bus -- consider the Hypnerotomachia painfully, tediously difficult.
And, in case you're wondering, the sex with buildings is on page 87. Reportedly, it was good for one of the buildings too.
My only complaint is that the British edition by Arrow books has pages that are too narrow, so it's almost impossible to hold the book flat on a desk or a reading stand.
I must see if the St. Andrews library has a copy of the Hypneratomachia Poliphili among its rare books.
UPDATE: We do have a copy, but I don't have time to look it up right now. Maybe later. Meanwhile, Manuscript Boy e-mails to point to a digitized copy online at the Jewish National and University Library. You have to install special software to access it, and the software works for me with Safari but not Firefox, but the images are cool if you can get at them.