Unsurprisingly starts to refute the idea that the Staff loafed about, did nothing, got the medals and had an easy war. Not exactly sure how you prove they didn't do these things, but the book has a good try.
20% of them were killed or injured, they did visit the front line frequently, not necessarily the Fire trench, but more likely Support or Reserve of the HQ.
Where they came from, Regular, Territorial or Volunteer. But regulars with psc dominated the higher ranks. Staff were scarce, their lives ought not to be wasted. Staff Officers were very much aware of front line conditions. They faced tremendous changes and challenges. The British Army changed from a small professional colonial army to a mass army able to prosecute all-arms warfare. The British and French Armies together achieved victory against a redoubtable foe. The work of the staff played a vital part in the Allied victory.