Heylin's big idea - that, under the influence of the counter-culture's relationship with "anti-psychiatry", British rock from 1967-75 was preoccupied with mental illness, and frequently created by those who suffered from it - is one of those ideas that, in hindsight, seems so bleedin' obvious you wonder why no-one picked up on it earlier.
His analysis of the roots of the phenomemenon, and the work which came out of it, is commendably thorough, thoughtful and reads very smoothly. He's particularly good on some of the less well-known works, such as "Jackson Frank", the more obscure corners of Peter Green's Fleetwood Mac albums, and the depressing tale of Vincent Crane. You could, if you wish, probably pick a few additional artists he could have covered, but there are no serious gaps.
Overall it's an interesting and engaging read, though it has a couple of flaws. Heylin's tone gets rather churlish at times - he's really got the knives out for David Bowie and the Nick Drake estate - and while his points may be valid he does himself no favours by writing about them in a style reminiscent of the people who used to write to the papers in green ink and make their obsessive points in CAPITAL LETTERS. More importantly, the book just seems to come to an end: there are interesting appendices, but the overall narrative arc ends abruptly, without any attempt to pull it all together, in chapter seven. There are a couple of hints that the punk and post-punk eras kept on this exploration of inner space, but more is needed, and in particular the roles of transitional figures like Peter Hammill and Richard Strange could have been used to show how this admittedly peculiar torch was passed on.
All said, though, a highly readable, stimulating and original book on a mysteriously overlooked aspect of music history.