Here's my response and don't forget to check the comments on the BTT site for everyone else's.
While I'm thankful for a lot of things in general, it takes more thought for me to decide what I'm thankful for when it comes to reading. Of course I'm thankful for the enjoyment that good books bring me, but that's too simple. What I'm really thankful for is the chance to lose myself in a book, to know characters in a way I can never know real people, to experience challenges and feelings that I wouldn't want to in real life, and find a happiness that can't be destroyed by anyone. Great books create something inside the reader that stands apart and untouchable by reality. I'm thankful for that.
And maybe it's a little off target, but I'm also thankful for readers. My readers, few as they are. When someone you know and respect tells you that they really like what you wrote it feels great. When a complete stranger does the same it's just as awesome. I'm thankful for those who've thanked me for what I've done. It's a good circle.
Finally, I'm thankful that I just crossed the 50k word mark on my NaNoWriMo project. I've still got a little ways to go to complete the book, but I'm thankful to have a community that encourages folks to do something as grand and ridiculous as writing an entire novel in one month. Good or bad writing, agonizing or exhilarating, it's all a wonderful thing.
Happy Thanksgiving everyone!