The Irony of Nocturnal Creatures
As Dewdney points out, there is irony in the situation of the nocturnal creatures who can see in the dark: the darkness is all about the light, as tiny traces of light are the mechanism by which these creatures can see in the dark.
The Irony of Night
Night is generally seen as simply the absence of the sun's light. Ironically, Dewdney turns this on its head: night suddenly becomes an entity unto itself, complete with its own beauties, dangers, and personifications.
The Irony of Reverse Personification
In the first chapter of the book, Dewdney includes several poetic excerpts that deal with night. Romantic poet Henry Wadsworth Longfellow, in his poem "Hymn to Night," personifies death as a woman - his lover, in fact. Ironically, Australian poet Frank S. Williamson flips this personification around, choosing to portray his lover as an embodiment of night, creating a sort of "reverse personification."
The Irony of Night Research
While writing this book in his study, the author pauses to realize, not without a bit of smugness, that while other researchers have to go out and find the subject of their research, his subject will inevitably just come to him: night will always visit him wherever he is, making travel and a search unnecessary. This renders half of his job as a researcher superfluous.
The Irony of Nightlife
As technology has progressed, humans have become increasingly nocturnal; using electric lighting has allowed people to continue their activities into the night, giving the night the opportunity to become just as productive as the day. Ironically, this practice essentially destroys night by turning it into an extended day, as it's being used in the same way a day would be rather than in its own unique fashion. Nightlife, therefore, is a misnomer; it's just daylife during the night.