Karin Slaughter and Lee Child got together to write a short story about Will Trent and Jack Reacher, and the result is CLEANING THE GOLD. If you're looking for a quick read, this could be it. I would warn, though, you should already be familiar with Will Trent and Jack Reacher to appreciate this story.

The two of them are both working undercover at Fort Knox, although, really, Reacher is only sort of undercover. Neither of them knows the other is undercover.

Reacher is there to find evidence to convict a known bad guy in the army who works there. Trent is there to get a DNA sample to catch Reacher. They think

I wondered how they could possibly work together, and I enjoyed it. But I think that is only because I understood the characters to begin with. They are so totally different they couldn't work together for long, so only a short story would work.