Charming and inventive
This is exactly the kind of story that you make up as you go along when telling stories to children, albeit of a fairly sophisticated and inventive kind, and that's apparently exactly how Mr. Bliss started, as a story for Tolkien's son. A man with a spiffy new car who keeps a girabbit (giraffe-rabbit) knocks over a man selling cabbages and a woman selling bananas (or possibly the other way round), picks them up, they get lost in a forest, almost eaten by bears, but the bears eat the bananas and cabbages instead, and so on and so forth.
I happen to love the Lord of the Rings too, but don't buy this if that's all the Tolkien you know and you're expecting the same Tolkien. But if you love the more eccentric and home-y bits of The Hobbit and LOTR, or the Father Christmas Letters, then this is exactly the right book for you. It's the kind of story you would expect a slightly eccentric academic Englishman to tell his children, and if that's the kind of thing that appeals to you, you will adore this book.