I'm not DoV but I would say the book was worth reading. Tommy Lascelles' career spanned multiple monarchs and gave him a rather unique, erudite and sometimes amusing perspective into their personalities and foibles.
I've read quite a few biographies on the BRF- in fact I swore off them because they all seemed alike, but recently DoV recommended Robert Hardman's Queen of the World, which has been a refreshing change, IMHO. He's used material from Tommy Lascelles' diaries quite a bit thus far, particularly during about South African tour in 1947. I'd not seen a lot of it before.
Just my two cents but I'm putting the book on my library list.
Can you imagine what a read it would be uncensored! Still waiting for my copy. My Lady C book arrived and was immediately swallowed into the my husband's home office. It could be a decade. Or at least until he goes back to his office ofice!