I read while riding my recumbant bike 3-4/week in the winter and break a sweat (I also check the heart rate on my machine and am in the range I need to be). I find the 30 minutes go by very fast when I'm absorbed in a good book.
We had 33.5 inches of snow last month in my neighborhood so outdoor biking is out
. Besides, then I'd have to pay attention! Haha.
In the summer I walk in the park and read with my reader. My local park has a one mile loop on a gravel path and I find it relatively easy to read and walk at the same time. I read The Long Walk by Stephen King last year which was very interesting to read while walking.