This is, in fact, an epic fantasy story told by the comedy sidekick. His first act is to steal a giant, who is set up as the comedy sidekick, but there is unsurprisingly more to him.
The setting is also pretty good; medieval-Euro fantasy, but Mediterranean, distinctly Spanish, with an El Cid flavor. No, it's not a Guy Kay history riff, and there's no religious/cultural backstory at all (conqueror wants power, is all). But it has a better, or at least more convincing, eye for battlefield tactics than most medieval-Euro fantasy. On the other hand, minus one point for the extremely McGuffiny talisman.
Sequel exists; haven't decided whether to get it.