but Kindle books are DRMed and iTunes music isn't.

...anymore. iTunes books have DRM. iTunes music had DRM for years. DRM is the way you get big media to shift business models. Without DRM they'll happily forgo the new revenue stream and die slowly. So you first concede on the DRM point and restrict content just to begin the transition to the new model. 10 years after Napster major labels finally allow (most of) their music to be sold DRM-free. Print publishers will get there too.

Only if you're buying them from Amazon. There are plenty of wonderful texts available in the public domain, and already formatted for the Kindle: http://manybooks.net/

That's actually why I placed my order: I won't abide by the DRM, which will force me to read older works to get value out of the device. A goal I've had since reading a quote dubiously attributed to Einstein: "Somebody who only reads newspapers and at best books of contemporary authors looks to me like an extremely near-sighted person who scorns eyeglasses. He is completely dependent on the prejudices and fashions of his times, since he never gets to see or hear anything else."