If there is more than one copy of the Qur’an in the house, is it obligatory to read from all of them, or is it sufficient to read from only one?

There is no harm in a Muslim reading from one or more copies of the Qur'an. There is no authentic evidence to suggest that someone who contents himself with one copy is abandoning other copies or is to be punished for doing so. The argument based on what Al-Qurtubi mentioned about Anas regarding someone who learned the Qur'an, hung up his copy, and did not review it, is not valid due to the lack of an isnad (chain of narration) for it.