Author
Martin Waddell
2 books here

Owl Babies
Picture book · ages 3–6 · 450L · 1992
The canonical picture book for processing separation anxiety—repetitive, rhythmic language + reassuring resolution makes it returnable for anxious kids without feeling didactic.

Can't You Sleep, Little Bear?
Picture book · ages 2–5 · 2001
The definitive bedtime book for toddlers — repetitive, rhythmic, and genuinely soothing; Big Bear's patient reassurance models the exact emotional tone anxious kids need at sleep time.