A slim one, and I never have known where to shelve it

What I've never been able to do with this book is place it, and I mean that literally as much as otherwise. It came to us as fiction, obviously. Then a run of sixth formers took it out inside a single term one year and all of them talked about it as though it were scripture, and for a while I had it double-carded, once in the fiction sequence and once with a note in the 290s, which I didn't do lightly and which the county adviser queried in writing.

The book itself is short and plain, and the plainness is deliberate; the German is famously simple and the Rosner translation we had is simpler still, occasionally to the point of sounding like a fable told to a slow child. I've read three translations now. The differences between them are considerable and nobody ever mentions it. The Penguin we finally settled on had a young man in silhouette against a sunset on the front, and I am fairly certain that cover did more for its circulation than anything in the text.

Two things in it are genuinely good and I'd defend both.

The first is Kamala. She oughtn't to work at all. A courtesan who teaches a holy man about desire is a device out of the worst sort of novel, and yet she is given more sense than Siddhartha has for most of the middle section. She knows precisely what he is. She knows he will leave. There's a moment where she tells him that he is like her, that neither of them can really love, and it's the only moment anywhere here where the hero is properly caught out by another person, and he isn't allowed to answer.

The second is the merchant stretch, which everybody skims and which is the honest part. He gets rich. He gets fat. He begins to care about dice. It isn't dramatised as a fall — no scene of ruin, no crisis with a capital letter, just a gradual and entirely recognisable coarsening in a man who has decided he is above being coarsened. Anyone who has watched a clever person go slowly wrong will know that mechanism, and it's far better observed than the mystical business at the end.

Now, my difficulties.

The son. Siddhartha's boy arrives, is unbearable, and leaves, and this is offered as the final wound and the lesson he needed. But the boy is a plot device with a temper. We're told he suffers; we are not shown it; and having spent the whole book with a man who abandons everybody he meets, we are then invited to be moved that somebody has abandoned him. I'm not moved. I think the book half knows and flinches.

Then there is Govinda, who exists in order to ask the reader's questions and to be marginally less enlightened than his friend at every stage, for forty years, without ever once getting annoyed about it. One scene of Govinda telling him he's insufferable would have improved matters enormously.

The river gets the last word and I still haven't settled what I think about the river. On a good day it's the finest image he ever managed: everything present at once, the voices, the om, the ferryman who says almost nothing for years. On a bad day it's a European gentleman in 1922 assembling a religion out of the parts he liked and leaving out every part that involves obligations to other people. Both of those are true at the same time. It's an eight rather than a ten for exactly that reason.

For a reader: seventeen or eighteen, someone who has started asking large questions and getting cross when they are answered badly. It is short enough to be finished, which matters more than anybody will admit; a good number of the books that change people are simply the ones brief enough to get through in a bad week. Priya took it in her upper sixth and told me later that she had argued with it the whole way and then thought about it for a decade, which strikes me as the correct result.

So where does one put a book like that? My card still has it under fiction with a query mark I pencilled there in 1983 and never removed.