I have a great fondness for Simon Raven, but his novels are very variable and later ones down right awful. This is one of his later ones when he was under deadline to write a lot . Describing it as problematic is to avoid saying that it is a farrago of tosh with dollops of nonsensical supernatural underpinnings and is only for the die-hard fan who is willing to overlook a mountain of logical and stylistic flaws.
The problem is that if you are going to write a book involving the supernatural it has to be done with the same honesty as, for example, writing a 'locked room' detective story. You can't just 'solve' it by saying, oh there was a secret door. That is cheating and while Mr. Raven doesn't exactly cheat his characters from being ordinary academics, for example, to credulous believers in 'spooky' stuff at the drop of hat. I don't mind Raven's descent into 'weird' storylines, it appeared in early books like 'Doctors wear Scarlet' but here it is crudely and carelessly done.