Board to Death TV reviews Thunderstone. Felicia gives it 7, and Steve 7.5 out of 10 and they summarize the game thusly.

What's Cool:
Over 500 Cards.
The deeper you venture into the dungeon, the harder it is for you to fight.
The "Light" concept is pretty good.
You build your deck as the game progresses.
You can use XP points to level up your heroes.
Defeated monsters give you gold, XP, and some give you bonuses as well.

What's Not:
The card stats are plain circles with numbers in them. (Most are purple.)
No real player interaction. ( It has a solitaire feel to it.)
Some cards will never be bought and are weaker then others.
The clean up can take a while.

Neutral Information:
It's a Card game, don't let the box fool you.

P.S. I have permission to post the Board to Death reviews at this site.