Hour of the Horde by Gordon R. Dickson ($1-$5 @ Amazon) is an interesting story. The basic plot is that one day the Sun turns red, an alien spaceship the size of Rhode Island shows up, and the aliens announce that the Horde is on the way, the Horde being one of those great alien races that consumes everything in its path (ala the Crystal Entity in Star Trek lore).
The aliens need all the help they can get, and of course if Earth wants to be saved it has to join in the fight. The rub is that we humans are too primitive to use their weapons, save one person who will be contacted shortly. Said person turns out to be an artist who is trying to learn to use something he calls overdrive, the equivalent of hysterical strength, in his creative efforts as an artist.
He’s somewhat taken aback at being this person who has to save his world of course (holy cow, right?). But before he can go off to join the fleet he has to be ‘charged’, sensitized to humanity on a broad scale. The aliens give him the ability to instantly go anywhere on Earth, make him invulnerable to everything including nuclear weapons, and say ‘off you go’. For a few days he wanders the world,just absorbing the various cultures,understanding how it all fits together, and then it’s off to figure some things out (it’s not easy) and finally do battle.
In the end the good guys win, and as you might expect from a Dickson book, it’s because of the human. It’s a good story, but I was taken by the idea of touring the world to be charged by all the various people. It reminds me of how much I learn from sitting and talking with people at SQL events, and how I always feel I’ve grown afterward. If you like science fiction it’s a good read, fun on the surface, but with some deeper thoughts that make it worth the time.