I picked this up second-hand as a counter to Edward Heath's autobiography, which I read some time ago. Both proclaim modest upbringings, but once Heath arrived at Oxford he writes as if he was destined; Callaghan on the other hand was brought up mostly by a single parent following the death of his father, and entered the civil service directly upon leaving school. Nevertheless he rose rapidly in the party following the general election of 1945, becoming a Parliamentary Secretary within a couple of years and entering the Shadow Cabinet in 1951. To date he is the only person to have held the four "great offices of state" - a position unlikely to be assailed in the foreseeable future (only John Major and Gordon Brown come close and I don't see any prospect of either of them returning to complete the set).
His autobiography therefore naturally divides itself into sections up to 1964, then Chancellor of the Exchequer, Home Secretary, Foreign Secretary, and Prime Minister (there is little material to speak of on Labour's period in opposition, 1970-74). The material on sterling crises and devaluation in the 1960s is particularly interesting, and the experience was certainly useful to Callaghan in later times. Shortly following devaluation he was moved to be Home Secretary in a reshuffle; the issues he chooses to write about here are clearly strongly felt, particularly on care of children and prison reform. As Foreign Secretary he dealt with the referendum on the UK's EEC membership, plus events in Cyprus, Portugal, Rhodesia, and a watchful eye on the Falklands. The final chapters, on his Premiership, provide a coherent an honourable case for the government's policies and actions in the mid-to-late 1970s. Callaghan does not deny there were disappointments and failures; I don't think it justifies being described as "bitter", but he doesn't shy away from pointing out the catastrophic consequences for the Left in 1979, in no small way self-inflicted by militant unions and activists. It has made me look differently on the Winter of Discontent.
Interestingly, one common theme between both this and Heath's book is the way they both imply acceptance of the political as well as economic aims of European union. Callaghan felt constrained by the divisions in the Labour party of the time from pursuing a stronger line.