best I've read, and actually the book I'd encourage people to start with if they haven't read any of Dame Ivy's fiction (love the author and understand her approach, and I think you'll be in the best place to try her novels) but Elizabeth Sprigge's The Life of Ivy Compton-Burnett (1973) is also pretty good...
Like Greig, Sprigge knew Ivy Compton-Burnett personally, which gives the biography a similar tone of friendly love for the author. It perhaps also explains why the chapters about her childhood and family are the least interesting - because Sprigge had no firsthand experience of them. Ivy Compton-Burnett had a staggeringly large number of brothers and sisters, and although plenty of events befell them (two sisters died in an apparent suicide pact; a brother was killed at war) I found this section far less interesting than the rest of the biography, and Ivy herself doesn't seem to have been particularly interested in her family, excepting the brother who died.
The most interesting part of the 'early years' is the discussion of Dolores (1911), published when Ivy was still pretty young (the age I am now, thinking about it), later disowned by her and generally considered to be pretty poor. Sprigge disagrees, and, while acknowledging the disparity between it and what she would later achieve, includes several contemporary reviews which saw Dolores as the promise of a new and talented author. It would be another fourteen years before Ivy Compton-Burnett would publish her next novel (Pastors and Masters, which, to my mind, is very much ICB-lite) but after that she was pretty regular - a novel every two years, essentially.
The formidable look of Ivy Compton-Burnett on the cover of this biography wouldn't encourage to think of her as a slap-your-thigh laugh-a-minute type, and Cicely Greig certainly attests to how thin-lipped she could be if anybody fell below her high standards of good manners, but in Elizabeth Sprigge's book it is definitely Ivy who provides the laughs (since Sprigge is not an especially witty writer.) For instance, this may not have been a deliberate witticism on Dame Ivy's part, but it is certainly amusing...
Margaret Jourdain had the gift of taking an interest in whatever interest in whatever interested her companions - an ability which Ivy Compton-Burnett did not share. If a conversation took a turn alien to her, Ivy would bring it to heel. For example, one day at a friend's tea-party a number of people began discussing a Russian icon hanging on the wall. Ivy listened for a few moments abstractedly, then observed decisively, "I do like a laburnum."Unsurprisingly, it is discussion of Ivy Compton-Burnett's writing and reception which most interested me, and this biography includes an edited version of a long interview which Ivy Compton-Burnett and Margaret Jourdain (a close friend who lived with her many years) compiled for Orion in 1945, which is essentially a discussion of her writing. And in turns out that Ivy Compton-Burnett is a very bad reader of her own books - or, at least, very different from everyone else. She does not consider her books to be very similar (they are) or her characters to speak in a heightened manner (they certainly do), nor does she think her writing is difficult to read (I suppose in one way it isn't, but Ivy seemed genuinely unable to see the difference in accessibility between her novels and bestsellers - Sprigge records many instances of Ivy Compton-Burnett bewailing her own lack of bestseller status.)
It is curious that somebody can write novels which, to my mind, are works of genius - and yet not be on the same page as her critics when it comes to recognising that genius. She certainly believed herself to be one of the best living novelists, according to Sprigge, but doesn't seem to have realised that it was her style and unique approach which gave her that title.
If, like me, you an avid reader of Ivy biographies, then I certainly recommend you get this one - let's face it, you probably have it already, there are plenty of copies about - but if you are toying with trying your first memoir of Ivy Compton-Burnett (or, indeed, yet to make her acquaintance at all), then please seek out the equally-findable Cicely Greig's Ivy Compton-Burnett: A Memoir.