Shape Capers by Cathryn Falwell

From chapters.ca:
Shapes! Circles, squares, triangles, semicircles, rectangles! What can you do with them? Anything! Everything! The only limit is your imagination. Come on! Let's go on a shape caper!

Round is a Mooncake: A Book of Shapes by Roseanne Thong, illustrated by Grace Lin

From chapters.ca:
From round rice bowls to square pizza boxes, a little girl's neighbourhood becomes a discovery ground of shapes in this lyrical picture book. The bright, whimsical art illustrates many Chinese objects, and a short glossary explains their cultural significance.

Color Farm by Lois Ehlert

From chapters.ca:
On this farm you can view animal ears and whiskers too. Lots of animals to be found, shapes and colours all around. Look at beaks and snouts with me. Make some more for us to see

Shapes that Roll by Karen Nagel, illustrated by Steve Wilson

From chapters.ca:
Some shapes roll... some don't. Some shapes stack... others won't. Some shapes lie down... while others stand tall. Circles, squares, and triangles, even ovals and diamonds, are endlessly and intriguingly entertaining in Steve Wilson's world. Karen Nagel's rhythmic text is brought to life by Wilson's troupe of uniquely- shaped characters.

Circle Dogs by Kevin Henkes, illustrated by Dan Yaccarino

From chapters.ca:
The circle dogs live in a big, square house with a big, square yard. See the dogs? See the circles? Mama calls them pooches. Papa calls them hounds. "I'm a dog!" says Big Sister. Baby is, too. And even the youngest reader will want to wiggle and bounce and dig through the day with the circle dogs... until it is time for bed. An inspired collaboration, a new take on simple shapes, a story to read again and again.

A Triangle for Adaora: An African Book of Shapes by Ifeoma Onyefulu

From chapters.ca:
In the center of Adaora's slice of "paw-paw" is a perfect star shape. She doesn't want to spoil it, so she and her cousin Ugo set off to find a different piece of fruit. As they walk, the children see all kinds of shapes: Uncle Eze's rectangular "agbada," musicians playing circle- topped elephant drums, a crescent- shaped plantain, even plants with leaves in the shape of a heart. Ifeoma Onyefulu's vibrant prose and vivid photographs are a charming introduction to both shapes and to Nigerian village life. Sidebars provide further details about the fascinating objects illustrated.

Bees, Snails, and Peacock Tails by Betsy Franko, illustrated by Steve Jenkins

From chapters.ca:
Come explore the hidden shapes and patterns in nature. The peacock's flashy tail is a masterpiece of colour and shape. A buzzing beehive is built of tiny hexagons. Even a snake's skin is patterned with diamonds. Poet Betsy Franco and Caldecott Honor winner Steve Jenkins bring geometry to life in this lively, lyrical look at the shapes and patterns that can be found in the most unexpected places.

A Circle is Not a Valentine by H Werner Zimmermann

From chapters.ca:
The first book in the Alphonse series deals with shapes. Alphonse, a delightfully wacky artist, attempts to paint a valentine but, by mistake, creates a square, a circle, and a triangle.

Mouse Shapes by Ellen Stoll Walsh

From chapters.ca:
What can you make with one oval, two circles, and eight triangles? Just ask three clever mice who even find a funny way to trick a sneaky cat.