Hippopposites by Janik Coat is a concept book that uses a simple and adorable hippopotamus to teach some basic opposites.
There are comparisons between small and large, clear and blurry, transparent and opaque, etc. As the book progresses, the opposites become sillier, including a front (the usual red hippo) and side (a thick black line).
This is a concept book that despite it's simplicity in design doesn't talk down to its audience. There's also enough humor and sophistication here to amuse the older reader too &mdash a parent, caregiver, or an older sibling who might be reading the book aloud.