This, and its sister book about the Western Front, are absolute musts for anyone researching their family history with FWW Royal Garrison Artillery gunners in it. When you've done the Medal Card and War Records bit on ancestry etc or at TNA, and got some idea of where and with which unit your Great Grandfather fought buy this book. Mine was on the Western Front and I traced his movements through this book as things ebbed and flowed. You might wish to check out Naval & Miltary Press who have done a reproduction of both books at a reasonable price. Also, don't forget to visit Firepower, the RA Museum at Woolwich, London. The librarian there is an incredibly helpful person with an encyclopoedic knowledge of all things artillery.