Kidnapped by River Rats when Catherine reviewed it on her blog, A Spirited Mind, and was surprised to find it at my library. As a person affiliated with The Salvation Army since birth, I'm kind of amazed that I had never heard of it. The book, published in 1991 by Bethany House Publishers, gives a brief exposure to the early days of The Salvation Army in London, England, and the persecution early Salvationists endured.
Jack and Amy came to London with their mother to search for an uncle to provide for them. When their mother dies, Jack and Amy are left to fend for themselves and search for a man whose address they don't even know in a city full of danger. After they encounter The Salvation Army marching past on their way to an open air meeting (not actually termed in such a way in the book, but that is what we in the Army would call it), they must decide if William and Catherine Booth are going to harm them (they are told the Army is "after their souls") or help them.
The book provides a fairly basic introduction to the Army. I believe more details could have been used to flesh out the historical perspective. Still, it was a slightly interesting tale and does indeed provide a fairly good picture to kids of what it must have been like to live in the 1880s in London in poverty. It also touches on the evils of child sexual trafficking, so the reader should be aware of that before reading it aloud to children. It will open up some difficult, but important, discussions. I probably won't be reading it aloud to my boys simply because I don't think they'd find it to be engaging enough to hold their attention.