... as was "Band of Brigands" by Christy Campbell (2007). It gives the complete, and harrowing, story of how the first men in tanks went to war. Well written, too. It's one of those books that I've hung on to, as it deserves to be read again. "From mud, through blood, to the green fields beyond". 10/10.
"Conscripts" (Forgotten Men of the Great War) by Ilana R. Bet-El (1999) offers an unusual take on things. By the end of WW1 almost half of British Army recruits were conscripted (well over two million men); and the upper age limit was raised to 56 in 1918! It is quite a scholarly work; and whilst I don't quite agree with the "forgotten" proposition myself, there is a load of interesting information in there. 6/10.
"Forgotten Voices of the Somme" by Joshua Levine (2008) is worth a read, as it contains eye-witness narratives (a great deal of it understated) from the collections of the Imperial War Museum. In fact, anything from the IWM is always worth a go. 8/10.
And lastly, for me the classic from that era was (is) "The First Day on the Somme" by Martin Middlebrook* (1971). Middlebrook was able to draw upon interviews with some of the survivors. As the title suggests, it deals only with that first terrible day. I can thoroughly recommend that one. I read it 36 years ago when I visited the battlefields myself. It probably deserves a re-read - and a re-visit! 10/10.
Written in a similar style, Middlebrook's "The Kaiser's Battle" (1978) ... about the German Spring Offensive of 1918 - the
Kaiserschlacht - is also good.
Understandably, there are a lot of good books about the Great War around at the moment ... and there are a few more that I could mention - but I'll give way now for others to make their suggestions.

*
Who was a Lincolnshire farmer, by the way.