For all their apparent disparity, Royal biographies have much in common with Chinese takeaways.
Szechuan pork might seem radically different to, say, chicken chow mein or hoisin beef, but you can be sure that all have been liberally seasoned with similar spices and drenched with soy; and no matter how initially filling they might seem, you'll doubtless be ravenous again within the hour.
Ditto the Royal biog. Whatever the principal ingredient - the Queen, the Duke of Edinburgh, the Prince of Wales etc - side-orders of family snaps and background detail seldom much vary.
With Penny Junor, you're sure of a tasty bite. A Royal biographer of more than 30 years standing, with close links to the palace, Junor has in the past been widely denounced for her anti-Diana stance, painting the self-styled People's Princess as damaged, manipulative and needy.
Her latest offering reiterates this view and has attracted much in the way of negative comment, with Diana's one-time lover Dr Hasnat Khan recently breaking his silence to state that, far from being mentally unstable, Diana was simply maddened by her husband's ongoing affair with Camilla Parker Bowles.
However Junor sticks by her assertion that Charles put his heart and soul into his marriage and returned to Camilla only when it had irretrievably broken down. Nothing new there; but Junor also acknowledges Charles's shortcomings. He can, she says, be autocratic, peevish and moody - even if his son and heir is more than fit for him, and gives as good as he gets.
Junor makes reference to Charles's father-of-the-groom's speech in Buckingham Palace last April, when he spoke of William as a teenager, stuck in his room playing music at full blast for hours; and of the two-fingered response he'd get whenever he tried to offer paternal advice about clothes, or tell him to stop slouching.
But such childish petulance was short-lived. Dispatched to boarding school aged just eight, William, already deeply affected by the tension between his parents and his mother's frequent emotional meltdowns, soon learned to keep his feelings to himself.
By contrast, his brother Harry was and continues to be much less guarded; perhaps too much so.
While William was keeping his head down as a student in St Andrew's University, his younger brother was keeping the redtops in headlines.
Indeed Harry's exploits, good and bad, are writ large in this intimate portrait of his older brother. Unlike the good and dutiful William, born to be king, Harry is free to live the kind of life of which his brother could only dream. Which, given his form to date, should prove very interesting, indeed.
An ideal candidate, then, for the best sort of Royal biography - tasty and spicy and endlessly moreish. Take note, Ms Junor.