I first read this under the English title 'Jenny' years ago and it remained in my mind - especially "When in doubt, wash" - and I have just reread it. My memory hadn't played ticks on me with the passage of time, and it remains the treasure I remembered from way back. All of Paul Gallico's books are wonderful, and no-one should miss 'The Snow Goose' and 'The Hand of Mary Constable' (sadly, I think out of print!). Also, his Mrs 'Arris series.
Gallico has entered the mind of the cat without destroying their integrity, mystery and independent natures - there's nothing Walt Disney about this book - and the way he writes is deceptively simple. You can read this book at face value and enjoy it as a 'nice' story, or appreciate it at a deeper philosophical level which is more rewarding.
More than a book about 'cats' for 'cat lovers', this book says a lot about humanity and the lack of it without without preaching. It creeps into your heart and head without any effort at all and, more importantly, without the cloying sentimentality that many writers about animals descend to.
Be warned, though! If you don't like cats, you probably will after this!