At the very heart of certain narratives is a lacuna, to which the reader is drawn ineluctibly, as the centre of a whirlpool of meanings. It may indicate something essentially unknowable, ineffable - the lacuna in the Old Testament is when God tells Moses I AM THAT I AM, which lets us know in no uncertain terms that this thing is not of logic or language, whatever it may be; the lacuna of the New Testament is Christ's three days in the tomb - we are not told anything about that, it is unknowable. Or this gap in the story may indicate simply something someone does not wish to tell us - the very heart of the matter, the thing of shame, the motive. Here the gap is a void or avoidance. Psychologically powerful avoidance fuelled by intense guilt makes a hair-raising narrative, as the reader, writer and protagonist gradually converge together and find themselves in the belly of the beast - two memorable examples from non-fiction are Fritz Stangl's horrible wrestling with his past as commandant of Treblinka in Gitta Sereney's series of interviews with him ("Into that Darkness") and Michaud & Aynesbury's interviews with Ted Bundy ("Conversations with a Killer"). In both cases we are caught up in the subtle and confrontational stratagems the interviewers use to get the monster to acknowledge an identification with the previous self who committed the atrocities. Stangl ferociously hangs on to the "it was just a job, a really really difficult job" line until he cracks - and how dramatic to read that a day or so after he finally - finally - admits that he was personally responsible for what he had done, he dies of a heart attack. Bundy constructs a way of describing his crimes by "speculating" about them in the third person, contemplating how the person who perpetrated them "might have been" feeling, of how he "was reacting inappropriately to stress in his life". He edges to the very rim of acceptance of guilt but can't manage the swan-dive into what we non-serial killers assume to be the cleansing waters of catharsis which await those who accept their crimes and seek atonement. 
 Alias Grace's story likewise is a stately sarabande of 550 pages around the central question - did she do it? Suspended from that mystery, the ponderous but pillowy narrative describes the life of Grace Marks in her own languid hyper-observational manner (a great fictional voice) and counterposes this with the fervid cavortings of the brain doctor sent to ferret out her great secret. He's quite a scream. 
 So anyway, this book is squarely in that genre I call Modern Victorian, in which the contemporary novelist writes us another great big Victorian story but being modern can put in all the filth and flesh, all the naming of parts which the real Victorian novelists couldn't do. It turns out, from what I've read so far, to be a great idea. Consider these - 
 1) The Crimson Petal and the White (Michel Faber) - completely brilliant and nearly 1000 pages too 
 2) The Quincunx (Charles Palliser) - completely brilliant and just over 1000 pages 
 3) Fingersmith (Sarah Waters) - yes, just about completely brilliant too 
 4) The French Lieutenant's Woman (John Fowles) - acknowledged by all to be fairly brilliant 
 Very glad to add Alias Grace to this select list and will be happy to grab up other Modern Victorians as they swim my way. 
 Alias Grace likes, in its modern way, to leave a lot of stuff unanswered and without chucking in a huge horrid spoiler here, I can't reveal why I think that part of the Central Revelatory Scene was pure codswallop, but that didn't make no never mind. Margaret Atwood's big book sails onward, sad, sumptuous, and very slightly sexy too.