What should I do about the pirated books and novels that I bought? And must I repurchase them as original copies to restore the rights of their owners, or would that be considered extravagance? And does the ruling differ if I haven't read some of them yet, or if their content contains transgressions?

There is no sin upon you for purchasing copied books and novels without your knowledge of them being copied; the sin falls upon the aggressor. You are not required now to buy an original copy or to destroy the non-original copies you possess, especially since your use of them is for personal benefit and not for profit. Some scholars have permitted copying for personal use, as indicated by Sheikh Muhammad Al-Uthaymeen.