If this review is choppy, uneven, and otherwise disjointed, it is probably because I just pulled my head out of this book, which suffers the same afflictions.
The precocious Rachel Finch, aged twelve, adores Kafka, steals library books, and is whisked off on time traveling adventures by a mysterious alien known only as S-Man to rescue or not rescue important literary figures.
The time-traveling bildungsroman is peppered with utterly forgettable characters. Rachel's fellow students amount to nothing but white noise and are indistinguishable from each other because no effort has been made to do so. S-Man is a rip-off hybrid Superman/The Doctor, and no effort is made to disguise it.
Rachel does find a friend in a girl named Rachel Fish, who also loves reading and may be cleverer and somehow better than Finch, which Finch is all too aware of, and says to herself, 'but S-Man picked me to go on adventures!'
This novel tries too hard to be clever and fails to achieve what it dreamed of. Much like the protagonist whose life didn't turn out as she thought it would, and who muses about the other Rachel, who would have done great things, this book is an almost, but not quite. And if the writer orchestrated that outcome, she's better than I give her credit for.
I have the sense that the author intended some grand metaphor - what it may have been escapes me completely; puberty, maybe? - about the relentless forward progress of time, tunneling ever onward, but this tunnel ends in a dead end.