Basically, this story elaborates on how Toby the toddler is stuck with Iris, his new sister who is getting far too much attention.
To this Goodreader this reads as a poignant story.
Although I'm shelving this story under HUMOR, that's not my experience of this book. However, some readers may get a real kick out of making fun of poor Toby, such as his toilet paper mishap.
The beauty of this tale is that it's big-and-wide enough to accommodate those who want to laugh at Toby and others of us who just wish we could give him a great big hug... and then some quality attention.
An alternate title for this book might have been, "Toby Starts Attending the School of Hard Knocks."