The series is written for kids approximately fourth grade on up. The books are about a family around the time of King Arthur. The family consists of Sir Cumference, the father, his wife Lady Di of Ameter, and their son Radius, who appear in four books, and each of them has a book that focuses on them. My sisters are 5 and 7 and they enjoy this series a lot as well although it has to be read to them. The illustrations are unique in that they look like pastels and paints, they are not sharp lines, but they illustrate the stories very well.
This is the first book and tells you about the family. If you enjoy shapes and geometry, this is a book for you. The King and the knight do not like the tables they already have, so they give Sir Cumference the job of trying to figure what type of table would give them more room so they don't have to shout across, and you can probably guess what type of table they need by looking at the title. Sir Cumference has Geo of Metry make tables of various shapes, octagons, rectangles, diamonds, and triangles, and each time the King or the Knights do not like them. I learned about shapes I never knew about in this book. I don't want to spoil the book so I'll stop there, but I rate this one a 7 out of 10.
This one is about Radius and Vertex, a young knight who gets a paper that has a rhyme:
" Form the solids and find their places, How many edges, points and faces? The shapes that make two will pass the test, But one that does not must be your quest. Three times as tall as its base is wide, the true King's future lies inside." The King has hidden a sword in a place that five knights do not know of. Whichever knight can find the sword will be the next king. So Radius and Vertex work together to find the sword in the cone. This is about faces and solid shapes that is *really* interesting. They had figured out that the sword must be in a cone, so they searched the castle for the cone and they did not succeed. They measured some stepstones that led out of the castle and they went underground and found each one hung underground into a cone shape. Then they had to figure out which cone held Edgecaliber, the sword. I rate this 7 out of 10.
This is a thriller. It's about circles and circumference, radius and diameter, and geometry. Sir Cumference is having lunch with his son, Radius, and he says, "Oh my stomach, it feels like fire!" So Radius has to go to the doctor, but the doc is gone, so he looks for a cure and finds a bottle that says "Fire Belly." "Father has fire in his belly." So he gives this to his father. Poof! Sir Cumference is a dragon. Radius has to go back to the doctor's lab and finds a bottle with a note on it, that says, " The Circle's Meausure: Measure the middle and circle around, divide so a number can be found. Every circle, great and small - The number is the same for all. It's also the dose, so be clever, or a dragon he will stay forever." He takes the bottle to Geo and Sym of Metry (twins) thinking, they measure all the time. He sees that the spokes of a wheel they have divides the wheel in two ("across the middle"). Then, in the kitchen, his cousin Lady Fingers was baking pies. He helps her with strips of dough, like the spokes of the wheel. As he finishes the pie around, he puts the strips on the outside (the circumference). That's not enough, and he needs part of one more strip. This gives him the idea of going back and using the wheel measurement to figure the exact number around the wheel, compared to the measure across the middle. He of course finds the number, and is able to cure his father. You can see how he does it if you read the book. I rate this 8 out of 10.
This is about degrees and angles of circles. Radius becomes a squire to be a knight. His father one asks to see what he has learned. Radius shows him his archery, horseback riding, etc. His master, D'Grees, approves of him to take on a quest to save the King of Angleland. Every knight that has gone to try and save him has never come back. When he leaves, his mother, Lady Di of Ameter, gives him a medallion, a perfect circle, that has degrees on it to give him courage. Radius finds a note (there are a lot aren't there) that reads: "Warning stranger friend or foe, Dangers wait as forth you go. You must make a Knightly Right, Finding next Big, Straight and Slight. One wrong turn means lost to all, In a writhing, screaming fall. Find the Right to reach the king or you will feel the dragon's sting!" (signed by The Brothers Zig and Zag). Radius enters into a room with a circle with a line through it in the middle. He hears a fluttering and a crash, and the medallion slips from his hand into the circle, and forming a 90 degree angle, points straight to one of the pathways. He cries, "That's the Knightly Right!" and goes through the pathway. There are various other turns and puzzles that the medallion helps him solve to get through a labyrinth, which ends with a dragon!
There are lot of twists and turns at the end that you don't expect, so be prepared. I rate this a 9 out of 10, this was my favorite.