Hilaire Belloc (1870-1953) interested me because of his pro-Catholic outlook; could he perhaps have been onto something? Or at least present an alternative view of reality?
Wilson's biography is a fairly straightforward chronological account from Belloc's birth during a thunderstorm to death as an eccentric figure with a large white beard hiding facial asymmetry caused by a stroke. Wilson's sources are mostly documents in Boston College, Mass., but he energetically corresponded and met people with such surnames as Asquith and LeFanu, and such abbreviations as SJ.
There isn't much in the way of Belloc's personal history of ideas. Unless a certain envy of people who'd made, or held on to, wealth, counts as an idea. Let me look at a few topics....
 Catholicism and anti-Catholicism. Belloc was of course Catholic in the western sense, not Greek or Russian Orthodox; so far as I can tell he had no liking of these. Hunting through Wilson's index, I could find no trace of Joseph McCabe, born in almost exactly the same year, an incredibly prolific author of whom Belloc was certainly aware. As far as I know, Belloc never entertained any doubts as to the actual existence of Jesus. His Catholicism must have been reinforced by G K Chesterton, a lifelong friend. (According to Wilson, Belloc retained all his friends throughout his life). I have a copy of 'Survivals and New Arrivals', an account of heresies old and new; it is interesting but of course any rationalist will be unable to take the philosophical side very seriously. He mentions Islam, and in fact wrote a bit about it - for example, Mediterranean pirates being just about a living memory.
 Wilson discusses Belloc's pamphlet battle with H G Wells over 'The Outline of History'; it hadn't occurred to me that Belloc would have been jealous of Wells's sales figures. Wilson rather takes Belloc's side over Wells. Belloc thought the theory of evolution (which everyone attributed to Darwin) was taken over from Lamarck. Belloc's knowledge of science was in fact pretty much nil.
 Belloc's book 'The Jews' (1922) is unique in British publishing, I think. It was clearly prompted by the 'Russian Revolution', in fact of course a coup by Jews with backing from Jews in the USA. I don't think Belloc ever doubted that 'Jews' were descendants of people in the Bible, although cracks in this belief existed at the time. Wilson treats this book with evasive disdain; he is not a courageous writer. Incidentally a later edition, with a new preface, was published by Belloc in which he praised the new movement in Spain - i.e. the Spanish version of fascism.
 Another side to Belloc was the meditative travel book - a combination of historical speculation with a suggestion of energetic striding and/or footsore plodding to inns, eating wholesome peasant food, and orating poems - they surely couldn't have been intended for silent reading. Wilson omits his 1904 volume 'The Old Road', an attempt (I seem to recall) to relocate the Winchester to Canterbury pilgrim's way. He also enjoyed sailing and wrote a long essay on Caesar's invasion of Britain considered from the point of view of tides and wind.
 Belloc took the French side in the First World War; he had been anti-German for years. Wilson does not consider whether the First World War was a disaster to be avoided by the British.
 Just a note on Freud: Belloc was unimpressed. If man has unconscious impulses, that's an end to all planning.
 On history, Wilson found G. G. Coulton (seven pages on him), a Cambridge Professor of History specialising in ecclesiastical history, who exposed Belloc's historical dishonesty (page 359). Wilson doesn't like Coulton ('dedicated humourlessness', 'none of Dr Rowse's generosity of temper', 'There was, of course, no answering Coulton on his own terms'). Leo XIII of 1899 instructed French clergy not to doubt aspects of the faith when considering history; Wilson (356) says Catholics 'would inevitably feel torn in their loyalties'. As an illustration, 'Survivals and New Arrivals' is online, scanned in by a Catholic organisation: part has been garbled to elide Belloc's sympathy for the Spanish anti-'Communists'.
So while Wilson has made a creditable fist of the narrative part of his book, it's a pity the intellectual component is so confined and locked-up.