As far as I can tell, Puzzle Quest came into existence when someone sat down and went "Fantasy RPGs are popular to the point that people have died playing them. Simple match three puzzle games are popular to the point that people waste hours with 'just one more game'. What happens if we combine the two?".
What you get is a horrendously addictive game that's eaten my brain for the past few weeks. The plot's paper thin, like most older/simpler RPGs, but the characters are still lively--although most of them are annoying and the player character knows it. My guy spends a lot of time going "...your majesty, you have a whole army and we're fighting the undead, why do you need
me to go out and escort a caravan led by a dwarf who won't shut up about how awesome his siege weapons are?". It's that little bit of self-awareness and snark that makes what would normally be a stereotypical plot designed to ferry you from one mission to another just a bit more interesting.
The game mechanics are incredibly easy (match gems for mana, bring enemy HP to zero, don't die), but there's a Final Fantasy-esque system of spells and equipment that you need to have in the right combination for maximum efficiency. There's also a lot of strategy involved in figuring out which kind of mana you need, what spells you need to cast, and how best to handle your foe's unique spells and abilities.
koilungfish has a couple of charts dedicated to analysis of the various spells, and while I thought this was rather amusing at the time I can now see why it would come in handy.
It's also intriguing on a psychological level. With a game like Bejeweled, you're only trying to beat it so you can get to the next set of gems that looks exactly like the first. However, when you're beating an "opponent" and trying to get enough experience to get to the next level and learn Heat Sink so you can fight Dulog the two-headed ogre, there's a lot more drive there.
It's a very fun game and I'd recommend it for anyone who has a lot of time on their hands, or wants to play an RPG that doesn't involve eternal level grinding or long cut scenes.
You know what else is addictive? Vegetable crisps. Especially parsnip ones. I love this country.