Yes, Sir Norman Bettison's book is mistimed.
And yes, it would be in bad taste at any time.
But it will do him no good.
Books about trains, or stamps, or (these days, as in former days) the Royal Family, are bought only by people who like trains, or stamps, or the Royal Family.
Books about the Miners' Strike are bought only by people who agreed and agree with the Miners' Strike.
And books about Hillsborough are bought only by people who feel very strongly about Hillsborough, as a lot of people in and around Liverpool, especially, still do.
Their strong feelings are not in Sir Norman's favour.
Even the slightly risqué books, documentaries and dramas about Royals are now fundamentally affectionate, with all protagonists either dead or extremely old, and with the latter not implicated in anything even mildly naughty.
No one would read or watch, write or make Why I Hate Trains, or Why Stamps Are Rubbish, or Good Old Maggie Gave The Miners What For.
Likewise, no one is going to read an account of Hillsborough by Sir Norman Bettison.