The Red Pyramid is a book by Rick Riordan. It is the first in the Kane chronicles series.
Rick Riordan has also written the Percy Jackson series. The Red Pyramid is aimed for 9-12 year old kids and into the teens.
It is the story of a 12 year old girl called Sadie and a 14 year old boy called Carter. Their lives are pretty normal.
When their mum died when Sadie was 6 and Carter was 8 they were separated and Carter travelled the world with their dad and Sadie was sent to live with their grandparents. They only saw each other twice a year.
One Christmas their lives changed completely. Their dad took them to the British museum and blew up the Rosetta stone.
This was when Carter and Sadie discovered the Egyptian gods were real. Later on they find out that they are hosting Horus and Isis. With their guardian Bast the cat goddess they set of on an adventure to stop Set the chaos god building a red pyramid to destroy North America and to save their dad.
With magicians trying to kill them this is harder than it sounds. When they get to the pyramid they defeat Set but cannot rescue their dad for he is no longer Julius Kane but Osiris.
In the end it turns out that Set was being used by Apothis the enbodiment of chaos. And they open a school for learning the path of the gods.