This has been sitting on my shelf for a while to read and I'm kicking myself for not getting to it sooner as once I started I couldn't put it down. It's a wonderful mix of AU WW1 with steampunk and I love the main characters Alek and Deryn. The author has mixed in a cast of real historical figures such as Tesla and Hearst against his fictional backdrop of Clankers and Darwinists. A great finish to the series although I'm sad this is the last book.