I would say avoid his books because hes a hack.
He gets away with it because 1) most sci-fi (especially in the past, it's actually made a lot of strides) is pretty bad in terms of writing....it's more about the strength of it's ideas and fantasy.
2) Ender's Game is "Twilight" for nerds. Ender (and to an extent, Val/Peter) is this empty vessel for Teens to pour themselves into. (come on..it starts with Ender bemoaning about how the big bad grownups are always lying to him)
I'd say read Ender's Game because it's an interesting enough book. You can safely skip just about everything else he's written though.
The only reason Ender's Game gets so much praise is because most people read it as a teenager and didn't notice how awful it is. It's basically porn for mal-adjusted nerds (it's the ultimate revenge fantasy) so a lot of it's young readers (hey, myself included) completely miss the high amount of WTF.
I mean come on, the book starts out with the premise that eugenics works. The twist at the end is predictable.
Theres a bunch of plot holes....and the characters are ridiculous. Ender is this absurd Jesus figure and everyone else in the book is a cardboard cutout that exists solely for the purpose of either getting knocked over or propped up by Ender.
The thing is Ender's Game does not provide any insight into children per se, it does provide a perfect example of how many teenagers like to view themselves though (misunderstood mesiah figures persecuted by a universally evil populace) hence it's popularity.
The whole Val/Peter thing is just embarrassing and sad...and you can imagine a lot of Card's young readers placing themselves in that role and imagining themselves as great orators who take over the world with their brilliant (though never really articulated ideas).
Only teenagers and someone like Card could be so naive/insane/ignorant of how politics work to find such an idea remotely plausible.
It has at it's heart the premise that everyone in politics is just dicking around doing nothing.... just waiting for someone who actually knows whats REALLY going on to shine the light on them...(despite my disdain of current politics, I have slightly more respect for both sides than that).
Understanding that and reading Card's blog you can see maybe his politics and writing aren't so divorced
The books only redeeming quality, like I said before, is the interesting ideas....
The battle school for example is interesting...the game is interesting (until Card ruins it...the game is actually a really good example of where, instead of making Ender brilliant he just made everyone around him really dumb.) The buggers etc are moderately interesting.
I've read a fair amount of his other work, and really he hasn't done much worth reading....stick with any of the thousands of SciFi authors who are much much better.