Jeff Connor's Philosophy of Risk serves as a great supplement to Haston's In High Places. Though Connor recounts many of the famous climbs of Haston in good detail, his book overall focuses on Haston's personal life, motivations, and psyche. It's quite a challenge to get to the bottom of someone so inward, especially posthumously, but Connor gathers a wealth of resources (including Haston's diaries and letters), and he interviews many of Haston's close friends.
Whereas Haston's book has a very controlled perspective, Connor is more balanced. Philosophy of Risk includes several perspectives when things get controversial, such as Haston's deadly driving accident or the 1971 Everest expedition. Also, Connor is more thorough about the things that Haston actually did, so a large part of the book takes place in bars, Connor includes Haston's Eiger Sanction work, and he includes more than a sentence (as in Haston's autobiography) on Haston's marriage. Connor will probably get in trouble, however, for ranking mountaineers throughout the book.
Connor includes details of Haston's three trips to Everest. Many of the details of the first trip are a paraphrase of Haston's book, but the 1973 and 1975 trips are original material. Connor includes a lot of controversy that didn't make into Bonington's very tidy official accounts (Everest: Southwest Face and Everest: The Hard Way). I also didn't realize Bonington was so democratic in his team configuration, nor that Haston cast the deciding vote on Whillans' non-inclusion for the 1973 attempt. This book also gives attention to many other Everest climbers, as Haston climbed or was friends with many of them. Though occasionally Connor goes out on a limb (such as Haston's interest in the supernatural), I think he does a good job of analyzing the man who was such a public figure, yet decidedly inscrutable.