h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Katherine was an impressive woman, but not as interesting as her colleagues.

'Onward and Upward: A Biography of Katherine S. White' by Linda Davis.
Davis wrote it based on extensive research and an interview with EB White.

'Onward and Upward in the Garden' by Katherine S. White
EB White published this after her death, to ensure his wife had a literary monument. I'd bet there's a lovely foreword by him about his wife.

'Poems and Essays of E. B. White'
White wrote to and about his wife a lot. His essay on Bryn Mawr women is based entirely on Katherine; his poem 'Lady Before Breakfast' is about Katherine; and his love poems are all addressed to Katherine.

'Katherine and E.B. White: An Affectionate Memoir' by Isabel Russell
She was their secretary for many years. Her perspective is a very different one. Evidence suggests that Katherine was always somewhat disorganised, but only one letter from Ross suggests that she was also bumptious or overbearing. Of course, Russell wrote when Katherine was ill, drugged, and suffering for lack of real work to do. So we'll never know.

'E. B. White: A Biography' by Scott Elledge. Naturally, it has a fat chapter about Katherine.

'Let Me Finish' by Roger Angell
Includes a minute but well-written chapter about Katherine. The best part was quoted in the entry, though.

Forgot:

'Here at the New Yorker' by Brendan Gill
Gill took a laughing observer's stance in regard to the Whites, which offended Katherine on her husband's behalf. (Probably a good deal of the reason why she despised the book so much.)