GrandDad 
Katie, Will, and the Global Detectives [EPUB ebook] 

This book is written for children who have cancer, a disability or are battling a serious illness. The heroine, Katie, has cancer, and sometimes is in a wheelchair. She has a friend, Robert P. Rabbit who can talk to her, and who she talks to as well. There are other characters in the book who also can communicate with Robert P. Rabbit, but they are only special people. Together Katie and Robert P. Rabbit have many adventures that a child who is ill can relate to. It can be read by a child with basic reading skills, and it lends itself to being read by a grownup to a child.