The Run-Out Groove by Andrew Cartmel

His first adventure consisted of the search for a rare record; his second begins with the discovery of one. When a mint copy of the final album by "Valerian"-England's great lost rock band of the 1960s-surfaces in a charity shop, all hell breaks loose.
Finding this record triggers a chain of events culminating in our hero learning the true fate of the singer Valerian, who died under equivocal circumstances just after-or was it just before?-the abduction of her two-year-old son.
Along the way, the Vinyl Detective finds himself marked for death, at the wrong end of a shotgun, and unknowingly dosed with LSD as a prelude to being burned alive. And then there's the grave robbing.
But he does find out what happened to the missing child, and it wasn't what anyone expected-or wanted-to hear.