I've not had a chance to look at it properly yet, but when I opened it I noticed on the first page a large signature, in pencil, reading "Monty Butler".
Montagu is a common family name (my grandfather was yet another), so I assume that this book belonged to a relation of mine - and besides, who else would want to read it? Looking through my family tree, however, the only Montagu I can find of the right date (apart from my grandfather, who always went by Christie) is HMB's nephew, Montagu Sherard Dawes Butler, whom I could show you looking slightly less weird but can't resist displaying in his full regalia as President of the Bombay Legislature (1921-22):
Montagu (or Monty?) Sherard Dawes Butler is known today, if for anything, as the father of R. A. Butler, the Conservative politician. To be honest, he doesn't look like the kind of unbuttoned person who would sign his books in pencil. Is there another Montagu I've missed? Was this a way of signalling his lack of interest in Uncle Henry's achievements? Or did the book belong, after all, to some quite unrelated Butler? If I find any further clues within, I shall post them here.