So many books, so little time!
Our son was a slow starter, but at 12, he now likes books much more. We still read to him sometimes just because we all like hearing the story together or the book is particularly long. It's kind of a throwback to when he was younger, and he loves it! Sometimes we'll trade off so he reads to us and us to him, which gives him practice reading loudly and clearly enough for others to hear--another good skill to learn.
I loved getting our son into series books. That way, if he liked one, you had more to draw from. He's 12 now, but at your son's age, he loved the Magic Tree House series, Magic School Bus series, Captain Underpants, Tales of Desperaux. He also loved any Roald Dahl books, Winn Dixie books, and the Spiderwick Chronicles. We've read all of the Harry Potter books to him so many times, he corrects us if we misread anything (ARGH! Time for him to read them himself!) We started those when he was about 8.
At 12, he really has enjoyed the Charlie Bone series and Stargirl by Jerry Spinelli which they read in class. And a new book that he says he likes even more than Harry Potter is The Eyes of a Raptor by Julie Hahnke. It's in the genre of Harry Potter, with special powers, etc. It's got great vocabulary-stretching words--enjoyable for kids and adults. The author has just come out with another book, too, called The Grey Ghost which he'll be reading shortly, I suspect.
Meanwhile, one thing that also got our son reading was magazine subscriptions. He's had about 5 subscriptions he's been given as gifts through the years. The ones he's loved the best are Your Big Backyard (now he gets Ranger Rick, which is by the same people for older kids), Boys Life (Boy Scouts magazine, he gobbles it up, especially the comics and jokes sections) and Kids Discover (my personal favorite). If you had to choose just one, I would choose either of the National Wildlife Federation magazines (My Big Backyard or Ranger Rick) or Kids Discover.
Personally, I thought National Geographic Kids and Highlights were a waste of money. The former had way too much advertising in it, and the latter was just plain boring to our son. But the other magazines he gobbles up when they arrive. He's even started reading my husband's Air and Space when they arrive (cool planes and stuff, y'know!) and our local newspaper on occasion to keep up on things.
Whatever piques his interest is probably the most likely to get him reading. Engagement with you always helps, too. We often end our days with us all reading in the living room. Sometimes it's for fun, sometimes it's for his reading requirements of at least 1/2 an hour each day. Or he reads at bedtime in his bed.
Another book he liked around 8 was Haroun and the Sea of Stories by Salman Rushdie. (Yes, THE Salman Rushdie. It's based upon bath-time stories the author told his 9-year-old son and was the next book after Satanic Verses--a little change of pace for him, I guess.) It's a kid's book and we all enjoyed the story and it's imaginative weavings and naming of characters.
I never had a thirst for reading till I was an adult. It's so fun to get our son engaged in reading at an earlier age. It's something he can take with him his whole life!