For this text:
... dreaming of houses uncluttered by reality, by half a lifetime of memories, perhaps.
What does this mean? It means that the one who was leafing through Country Living magazine was dreaming of houses uncluttered and comparing it to his house in his reality? And perhaps in his half-a-lifetime of memories?
The context is excerpted from David Mitchell's novel The Gardener (my emphasis):
Satin white, Persian purple, oil-paint yellow. When I planted these birches they were broomstick-height, and now look at them. They tap our bedroom window on stormy nights. Hyacinths on (what I fondly call) my rockery. Boy-blue and girl-pink. Through the kitchen double-doors I watch you eating supper – carrot and coriander soup – and leafing through Country Living Magazine, dreaming of houses uncluttered by reality, by half a lifetime of memories, perhaps. But my, how well you look. White hair endows you with the demeanour of a friendly witch. Our geriatric radio – a wedding-present from my brother – is twittering away to itself.