We expect a lot from the man who wrote 'Hawksmoor' and 'London, A Biography'. We expect, in fact, a lot better then this. If this were a first novel by an unknown writer, I suspect it would have sunk without a trace. It is reasonably entertaining in a pot-boiler sort of way, but it is severely below par for the master.
The characters vary, and some are caricatures; others fail to round out into real people. The research is lacking. If you are going to set a book in a particular expert field - a field in which there are a lot of very well-read and interested amateurs - you had better get it right. No-one knows better than Ackroyd how to bring a world to life, to pull us into the spell of time and place, but here he stumbles. Dorset is never conjured up in the smoky reality which London assumes beneath his pen (OK, word processor) and the description of Neolithic archaeology and archaeologists is embarassingly inept. One comes across so many howlers before one is far into the text that archaeology buffs had better leave this one severely alone. Probably astronomy buffs, too. Not a subject I know much about, but even I know that a light year is a measure of distance, not time.
Curiously enough, this isn't the first time I've seen an author come severely a cropper using archaeology as a setting. This is odd, because unlike some expert fields, there is an awful lot of popularised stuff out there, easily accessible. An author doesn't have to spend weeks in the British Museum library, they just have to turn on a television. Ackroyd should have known that many of his readers, lured to the book by a setting they were interested in, would be in a good position to know whether he'd got it right. Was this arrogance or just sloppiness?