Pen & Sword Books - £25
Actually, the vast majority of this book is a re-print of Geoffrey H Malins's "How I filmed the War". The only original content here is Section 1 which takes up a mere 44 pages of the 344 page total. So somewhat disappointing that there is so little background to what has become regarded as iconic footage over the years; and of that background there are a number of pages taken up with an overview of the Battle of the Somme itself.
If you didn't already have a copy of Malin's book then this would be worth buying. Other than that, much of the information contained in section one - and more besides - could almost certainly be gleaned online.