Coincidentally, my listening on the train yesterday was the abridged audiobook version (.co.uk, .com) of his 1997 autobiography, Who on Earth is Tom Baker? (.co.uk, .com) which I remember frenziedly skimming shortly after it was published on one of my rare visits to England (I was living in Bosnia at the time). I remember the book being rather depressing, as he put his melancholic side very much on display. The audio abridgement has, I think, got a decent balance between humour and morbidity, to the point that I was laughing out loud, to the dismay of fellow passengers.
There's not a lot here about Baker's time playing Doctor Who. There is a huge amount about his childhood and early life, hilarious and moving: the Liverpool Catholic education, the years in a monastery, the unwise early marriage, nursing his awful father-in-law through a final illness, the efforts to find work in London; also teenage masturbation, and a failed erotic scene in his first film appearance (playing the husband of the Wife of Bath). And towards the end, reflections on age, celebrity, and the confusions that sometimes arise therefrom: I've snipped one such anecdote here.
Anyway, definitely worth picking up if you can find it.