I think the phrase from 'Constructions' that sums it up best is, 'The metaphorability of the universe is bottomless'. Frayn dwells on the preponderance and importance of metaphors, which he describes as modes of perception. This short, fascinating book is concerned with how human beings perceive the universe.
I found it a lot easier to read than I expect philosophy to be, and also oddly calming. Frayn handles huge metaphysical questions with gentleness, so as to provoke contemplation without causing pain or confusion to the brain of the layman. I particularly liked the sections on dreaming, which captured the combination of ambiguity and certainty associated with remembering dreams more effectively than anything else I've read on the subject. For instance, 'The dream disappears not only as we put it into words, but even as we attempt to recall it inside our own heads.'
What struck me during the section of the book that discusses the role of metaphor in language was the link to China Miéville's novel 'Embassytown'. In that, a race of aliens speak only a language that is utterly literal and precludes lying. During the novel this race is introduced to the concept of metaphors, which fundamentally and irreversibly changes their nature. Miéville seems to be effectively operationalising Frayn's point of view, although I have no idea whether 'Constructions' was in fact an influence.
I would describe this book as exploratory. It wends its way obliquely through a series of points, illustrating with anecdotes as it goes. I very much like the starting point that by perceiving the world around us we read it; bibliophiles like me are easily swayed by reading metaphors. 'Constructions' is definitely worth reading if you wish to contemplate your relationship to the universe. I also recommend it if you wish to be distracted from a headache.