Sam And The Firefly is a picture book by children's author P. D. Eastman published in 1958.
It's a story of an owl who longs for friends in the night when other forest animals are asleep. He finally finds a friend in a firefly named Gus and they both have fun by spelling out words in the sky making them glow with Gus's tail.
I came across the following reviews about Sam and The Firefly that I think you would like to read:
"The story of an incredible twosome that "provides interest, suspense and word repetition. Illustrations excellent" - School Library Journal.
“There’s a lot of P.D. Eastman on this list, but this was my favorite, mostly for the color of nighttime and how soft his illustrations are in it. Because it’s about two characters who fly, things are seen from the sky a lot and roads and hills just fade into the distance and it’s so great. If I ever make a night time book, it will rip this book off hard.” - Jon Klassen.