John Terraine does an excellent job of recording Douglas Haig's military career literally from his birth in 1861 to his death in 1928. He covers all the major campaigns Haig was involved in including the Nile campaign and South Africa. Part Two deals with the early battles of World War I, but the vast majority of the book (Part III) deals with the campaign in WWI directed under Haig as Commander-in-Chief. There is also a short epilogue on Haig's life after the war.
It says on the back of the book that Haig remains one of the most controversial figures of WWI. As Commander-in-Chief of the British Army on the Western Front he has been held responsible for the massacre of hundreds of thousands of his own soldiers in the muddy killing fields of Ypres and the Somme.
Undeniably WWI was an extremely bloody affair, but I should think that that charge could be laid at the door of every Commander involved on the Western Front. Haig had a rather bad relationship with David Lloyd George so it doesn't surprise that the PM never had anything positive to say about Haig. Besides, the chap was a politician, which should speak for itself. The one message I took home from the book is that the British Army most of the time was rather under-equipped and understaffed. Yet Haig still managed to beat the enemy in the field. So he can't have been all that bad.
As I said I found the book rather excellent but at times it can be quite a gruesome reading.