Time For Bed by Mem Fox and Jane Dyer is a very sweet book with wonderful illustrations. It's a book where on each page a Mommy and Daddy animal says goodnight to his/her baby.
The sentences are short and they rhyme, making it pleasant for baby's ears.
I'm sure the hardback version is much more beautiful. But these days, we love buying books in small version form which can weather bending, throwing and chewing.