For me, it depends on the type of book. I find I can bare reading a technical book online. However, I have trouble reading it for very long, I find myself skipping prose to get to the meat of the content, and I find a quick glance at my email or F5 on my favorite news site is just a small click away. Still, I personally find reading technical books easier on the computer while reading a novel or biography far better with a cup of coffee, an easy chair, and an e-reader.