Not too in depth and often really clunkily written, but it makes up for it by being, well, not too in depth and rabidly enthusiastic about the subject. Much use of the delighted exclamation mark. ("Maybe soon there will be no more cars!") Wolmar also pays a lot of attention to the experience of being a railway traveller throughout history - times, conditions, classes, stations, food, etc. It's unusual and much appreciated.