This is the first of Pratchett's "Johnny Maxwell" trilogy that I read (despite it being the third in the series). Honestly, it took me a while to get into it. I think that I would have done well to read the other two books first, although Pratchett's books generally stand alone and do not have to be read in any particular order.This was an entertaining read about a 13-year-old boy and his friends, who discover that the local bag lady's shopping trolley is actually a time machine. They travel back in time to see their town on the eve of an accidentally WWII bombing and, of course, meddle with events so that the future is changed.The characters were well-drawn and sympathetic. Pratchett's trademark literary humor is found throughout. As is often the case with his books, the better-read you are, the more you will enjoy this novel.