We always associate the word ‘book’ with printing, and think of it in terms of format and typographical convenience, but such mechanical criteria do not apply to notebooks, whose beginning and end are determined only by the unity of the poetic impulse which gives birth to a given series of poems. In other words, a notebook is the same as a ‘book’ in the sense in which it was understood by Charents, Pasternak and M. himself. The only difference was that M. did not have to stick to some particular length or structure – often artificial – which is required for a published book. But the word ‘notebook’ itself, as I have said, arose in our usage quite accidentally, owing to the fact that we were forced to write in school exercise books. It has the drawback of being too concrete in its meaning, as well as reminding one of Schumann’s ‘Notebooks’. The only thing in its favor is that it faithfully reflects the way in which we had been thrown back into a pre-Gutenberg era.
(Hope Against Hope, p. 193)