I read this a couple of years ago, and wrote elsewhere about it immediately afterwards, when I had the book still fresh in my mind. I thought I should save my thoughts on here.
I think this is probably the best book I've read in the last 10 years. It had an extraordinary effect on me, and was a total joy to read. The fact I read it in 2 sessions, after failing to finish a book in 3 months, is some indication of that.
Not surprisingly, I disagree with many of the comments above. There's so much in this book that many seem to have missed.
It's a book about time and memory. As such its obvious forebear is Proust, who is very consciously referenced more than once in the first ten pages - Austerlitz and the narrator meet in the Salle des pas perdus, an echo of 'temps perdu', and Austerlitz refers to the buffet barmaid as the 'goddess of time past.' But I feel that what Sebald does in this book is the opposite of Proust (the little I've read of the latter) Rather than, as Proust does, almost stopping time by focusing in on an individual moment and analysing it for pages, Sebald moves with pace through time, jumping backwards and forwards, making links that become more apparent as they accumulate.
The particular reason I like the structure of this, an apparent rambling narrative, is that it reflects the way I have conversations, jumping from one theme to another as inspired by a key word or thought. More relevantly, it's how memory works, leading you from one thought to another without apparent direction, the only theme being the path in retrospect through those thoughts, like an Alasdair Cooke letter or an episode of James Burke's "Connections". But, as with bopth those examples, the unifying theme is made apparent at the end.
I disagree that the narrative voice, of Austerlitz, consists of one emotion, or rather that that is a weakness. I was in tears several times while reading this, so powerful was it. It's a book not just about repressed memory, but repressed emotion. Austerlitz has been brought up by austere Calvinists, forgetting his infancy, and then become a dry academic. The narrative voice is appropriate to that, and his search for his history is also a search for feelings long lost - memories of his mother, even his native language that resurfaces in talking to Vera.
Why the double narrator device? I can think of several reasons. Principally because of the usual problem of how the story as told by the narrator came to be written down in the format the reader encounters it. The nature of the narrative is fluid, moving from one theme to another in a way that reflects intense conversation. If Austerlitz had decided to write his memoirs - which adds another problem of character intent - he would have structured them and created order. With the form of a 'narrator' simply retelling Austerlitz's conversation, there's an impression of a lack of structure - although of course it's intricately designed - exacerbated by the lack of any normal literary structural devices - paragraphs, chapters, headings.
Continuing the themes of memory brought up by the book, and linking in to the 'psychogeography' as mentioned by LFF, referencing Ackroyd although I think Sinclair is probably more relevant with the term, which I don't believe applies here. I don't think Sebald is interested in spurious mystical properties attributed to buildings because of the memories of past inhabitants. His concerns are more concrete. The buildings mentioned by Austerlitz all have direct relevance to his story, although when he first mentions them he's not aware of this. There are 4 railway stations discussed at length - Antwerp, Liverpool Street, Prague and Austerlitz. Liverpool Street and Prague are the end and starting points of his journey as a 5 year old. Antwerp is the centre of Austerlitz's obsession with stations and railways, although he isn't conscious of why; and of course Austerlitz represents him, not just in name but more symbolically. In addition, the forts discussed in the first pages are exactly the same design as Theresienstadt. I have a problem with the last, as, while Austerlitz's obsession with station architecture can be explained from repressed memories, he was unaware of his mother's incarceration until he got to Prague. Unless the suppression allowed him to link stories of the evacuation from Prague that he came across in his general reading to his interest in fort architecture, without understanding the significance of the link.
These stations are not just repositories of memories of passengers who have passed through them, as they might appear, which would be a tenuous and lazy metaphor. They contain Austerlitz's own memories. And the Gare d'Austerlitz, naturally, is the central repository, or should be. The metaphor of a library for memory is of course equally lazy, but more directly appropriate, and Sebald extends it in a way that's directly relevant, and provocative. The Bibliotheque Nationale, that's been built upon a site near the Gare d'Austerlitz, is railed against by Austerlitz, not just from an architectural perspective, but for its folly. But the underlying message is clear: The National Library is the representation of modern memory, it's where Austerlitz goes to find his own history. And it's been built upon the location of the warehouse that stored the loot of Parisian Jews, now lost. The symbolisation of that, that modern memory, efficient, shiny, erected to the glorification of a vain President, supersedes the memory of one of the great tragedies of the city, literally buried under its foundations. Similarly his efforts to find documentary evidence of his mother's imprisonment are restricted to an abbreviated Nazi propaganda film - memory is sanitised, edited, repackaged to serve the interests of those in control. Austerlitz's repression is symbolic of the suppression of the collective memory, his blackouts of the selective amnesia of society.
I think this book is hugely significant, and it will grow in stature with time. It's a tragedy that Sebald died only months after it was published, but I suppose that's preferable to him dying before. There's a vast amount in it that I haven't picked up on - the long Marienbad sequence for example, which plainly has significance beyond the river Auschowitz. Given the mention of Alain Resnais a few pages later, I presume it's a reference to his film L'Année dernière à Marienbad, which I'm just about to watch, and I understand is about the unreliability of memory. More significant of course is Resnais's film Nuit et Brouillard, a short documentary of Auschwitz, the unmentioned place that haunts the book, the final destination for the train that took his mother.