Under a Mushroom by Anita Lobel

This book is about a family of trolls, who live happily under a mushroom. When it starts raining heavily, they get some company. Then more, and more... A party starts, but then things get a little too crowded, and it's not much fun anymore. But - more mushrooms come up in the rain, and by morning, all the guests find a place of their own. Peace is restored, and lots of neighbours is good! They all live happily (under their mushrooms...) ever after, one would hope.
My copy is old and tatty, but I wouldn't part with it. I love the naive story and illustrations - so very 1970s in style. Who wouldn't fall in love with these pictures?