Sister Agatha: The World's Oldest Serial Killer by Domhnall O'Donoghue

There is a certain and rather peculiar fiction subgenre out there about the quaint adventures of unusually old people. Presumably there is an audience for it. And to be fair, a lot of old people are great and way better than new ones, so …
In terms of age, you can’t beat Sister Agatha. She’s 118. Remarkably spry for her years too. Still, she is only the fifth oldest person in the world, and when she erroneously comes to think that she only has a week to live, she decides to go out on top as it were, by killing the other four contenders for the longest-lived throne.
Yes, it doesn’t make much sense, but this is about quaintness and cuteness and whimsical Irish charm, not logistics. And so, Sister Agatha embarks on a globe-trotting adventure with a murderous gleam in her eye. 
True to the very impetus of her quest, what follows is also a comedy of errors, but she gets to go to exciting faraway places for the first time and meet all sorts of wacky characters. So, it’s fun and funny in a rather lightly amusing, inoffensive sort of way, and makes for a pretty quick and entertaining read. All in all, not too shabby for a random Kindle freebie. And right enough for April Fool's Day selection.