This comes up in children's reading evidence as a popular book in the 1920s. Adults talk about it as a "dime novel alternative." It's one of those classic books that talk constantly about how immoral the character is for running away to the circus and how much he regrets it, while reveling in the circus atmosphere, the monkeys, horses, elephants, circus freak show performers... Toby is indeed a bad and remorseful boy who, at the end of the book, happily rejoins the minister who took him in when his parents died. But along the way, you get an adventuresome ride through circus life.
This was first published in 1880, but the edition I have is 1923, and there are "shadow" illustrations at the bottom and side margins of many pages, in a mustard yellow color that belie the tension in the text. While the text is all about Toby's remorse, the illustrations show circus performer, animal and human, in exciting costumes and doing daring tricks. Nowhere is Toby's sorrowful face portrayed in the illustrations.