Alcatraz at first glance appears to be your typical teen-age boy, even if he's named after a world-famous prison. Being passed around the foster-care system hasn't helped his attitude much, though, and it seems that he brings it on himself with his terrible clutziness.
On his thirteenth birthday he gets a strange--and very old--package in the mail from his father (where is he? is he dead? is he alive? we don't know?) claiming that it contains Alcatraz's inheritance: a bag of sand. Mystified and sad, he decides to make himself some comfort food but accidentally catches the kitchen drapes on fire.
Then everything hits the fan: the sand is stolen, a man claiming to be his grandfather shows up, his foster mother wants to kick him out of the house, and a man with a gun threatens his life. Not a great way to spend a birthday, if you ask me.
But, oh, what hilarity ensues. What's great about Sanderson's stuff is that it's beyond the typical fantasy-epic-journey type story like you'd find in Paolini or MacHale. Almost the entire story takes place at the downtown library, where things aren't always what they seem. And nothing is off-limits: Sanderson makes fun of everything and it's just plain funny. Exceedingly silly, but funny for kids and grown-ups.
The characters are fun, and even the antagonists turn out to be complex people. Alcatraz in particular is an interesting character who struggles with his accident-prone nature, until he learns it's a 'Talent' (his grandfather's Talent is arriving late to things...it's so funny, but it works!). He's convinced he's a bad kid, but it gets harder for us to believe it as the story progresses, and even he seems to change his mind a little near the end.
Sanderson's strength, as in his other novels, is his plotting. He knows how to tell a story at a great pace, that moves forward and never lags. The author is also great with magic. He finds new ways to make magic just plain cool, like the Allomancers in
The Final Empire (Mistborn, Book 1). In Alcatraz the protagonists have their Talents (his cousin's Talent is tripping), but they are also Occulators--that is, many of their powers come from the eye-glasses they wear! How cool is that?! Having worn glasses all throughout my childhood, the idea of them giving superpowers is cooler than cool.
Alcatraz would be great to read out loud to your kids (I'd say ages 9-12), and you won't be bored in the process!