We've probably all seen a few authors providing free books for self-isolation. Smashwords has provided a central point for finding a lot of them. Some authors are using it as an excuse for a discount sale because they have the choice of how much to discount, but the ones who really care are going free.
My favourite time travel series I'm always going on about is all free apart from the last episode that isn't released yet.
A Fantasy trilogy I really enjoyed.
A two-book collection that starts with a sequel to Oliver Twist, following the Artful Dodger.
A light Mystery set in a circus.
If you don't have an ereader, they offer PDF among the formats. All completely free. You don't even have to sign up, just instant download.
You could spend hours just browsing through all your favourite genres.