I've skimmed through the reviews and scoured the personal comments, and carefully organized some key quotations to bring you the important things you need to know and what other people think about Shazamm!. Perhaps you could call this a kind of "consensus of opinion" - biased of course, because I'm the one who gets to pick the quotes to include. Nevertheless, here you have it, an at-a-glance overview of some of the majority opinions that you need to know about this game.

1. The components are good.
"The game is very colorful, well-made and intuitive, all of which makes explaining the game and actually playing it very easy."
"Let me give an extra nod to the fine quality of the components. The cards, board, and wizard pieces are all very colorful and eye-catching."
"Very nice components."
"Great Z-Man presentation: slick, beautiful comic art and the bidding wheel looks cool."
"Excellent packaging and components."

2. It won't appeal to everyone - the gameplay revolves around resource management, blind bidding and bluffing, and is a matter of personal taste.
"At its heart, this is all about effective resource management and predicting your opponent's moves."
"This is essentially a game of resource management and bluffing."
"Unfortunately, I am not a big fan of blind bidding and double guessing."
"If you like both Blue Moon and LotR:C then chances are you'll like this game"
"Blind bidding, hand management, and spending your resources wisely while trying to outguess your opponent. "
"Clever 2 player card duel. There is a surprising amount of depth with the interplay of the different card effects. The whole game is based around bluffing & guessing which cards your opponent has played."
"Shazamm is an outguess-your-opponent game with two levels of guessing. Ideally, you either want to commit one more Mana on a round than your opponent, or you want to commit a lot fewer Mana, so you'll have more toward the end of the round. You also try to outguess what spell or spells your opponent will play, as certain spells neatly counter others. If you enjoy games where you try to read and outbluff your opponent, then you'll love Shazamm. "
"The mix of double-think and situation analysis is interesting, and gives a satisfying game."
"I love the theme, the bluff and double-bluff aspect, the card combos."
"Some of the comparisons to, say, head to head poker are at least somewhat valid."
"Outguess-your-opponent game with magic spells for additional level of complexity."
"Two-player blind bidding with special power cards thrown in."

3. The apparent chaos diminishes over time, and the game improves with repeated play, especially with the same opponent.
"Seeing your exemplary plans foiled by an opponent's card is frustrating, but the game's theme and fast pace prevents this from being a real brain burner."
"One of the truly great two player games. Sure there is a lot of chaos, but less than in poker."
"Long term strategy, hand management, outguessing... this game is pure adrenaline, I love it...Those who say it is just a series of uneducated guesses have clearly failed to grasp the subtlety of this beauty which gets better and better the more you play (especially with the same opponent)."
"I've played this game about five times with a few different opponents, and it seems more enjoyable the more you play with the same partner."
"Rewards repeated play by opening up more play depth than is apparent the first time you sling spells - those who say there's little control to this game are just plain wrong."
"On first reading it seems a totally random guess-fest. In play, that is rarely the case: the interaction of the spells (more so the ones played and therefore out of the game) and board position set fairly stringent limits on what each player can do."
"Particularly fun after a lot of games with the same opponent."
"Initial plays might seem pseudo-random as the spells can seem arbitrary and the amount of mana quite high. But with repeated play comes knowledge of the various combinations that can be used and how to use them. The nice twist/challenge in the game - Cards will only be used once and you get them in a random order - starting with 5 and gaining 3 more after each round. Part of the challenge is doing well with the cards you have."

4. The bottom line: what you need to know.
If you enjoy games with blind bidding and bluffing like Lord of the Rings The Confrontation, and don't mind a fantasy theme, Shazamm! offers a good quality two player duel that will be best enjoyed with repeated play.

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The complete list of Ender's "What you need to know and what people think about..." reviews:
http://www.boardgamegeek.com/geeklist/37595