Learn Italian: L'autore stesso non aveva una copia. - The author himself did not have a copy.

The placement of stesso changes its meaning entirely. When placed before the noun (lo stesso autore), it means "the same author". When placed after the noun, as in this sentence (l'autore stesso), it provides emphasis, meaning "the author himself".

Could we use medesimo in this sentence instead?

Yes! You could say L'autore medesimo non aveva una copia. It means exactly the same thing, but medesimo has a slightly more formal or literary tone compared to the everyday word stesso.

If the author were female, how would the subject change?

The female equivalent of l'autore is l'autrice. Because stesso acts as an adjective here, it must agree in gender and number with the noun it emphasizes. Therefore, the phrase would become L'autrice stessa.

Why is the verb aveva in the imperfetto tense rather than the passato prossimo?

The imperfetto is used to describe a continuous state or an ongoing situation in the past. Here, the author simply "didn't possess" a copy during that general period. If you used the passato prossimo (non ha avuto), it would sound like a single, completed event, such as "he didn't receive" a copy on a specific occasion.