It's the adventures of a self-professed arrant coward who keeps on -- completely by accident, he assures us -- getting himself cast into adventures and playing the role of hero. He always has an explanation for his acts that appear heroic, but the intriguing part is that maybe one time out of ten, he is explaining to the other characters how he has to do this (which is the safest thing, he thinks), but nine times of ten, he is explaining to the reader that the apparent heroism was self-interest -- and when that fails -- well, once he and other soldiers were under attack in an underground complex. They blast a hole through the wall, he and another escape, and the walls collapse, trapping the others. Cain says he must have been in shock before admitting that he threw himself at the collapse trying to dig through to the others.
Everyone else thinks he's a hero. This is because they always see him acting heroically and never in a cowardly manner.
What I find particularly intriguing is that it is a retrospective account by Cain. Or rather extracts from it by another character who features in some of the tales. She writes that she has let the main account stand, but puts in explanatory -- or justifying -- footnotes on occasion, and interpolates excerpts from other works when she thinks Cain's doesn't explain everything.
(scurrying off to read Cain's Last Stand)