Best if of course very subjective, but I have read A LOT on my laptop.
Two things that for me are absolutely crucial for normal laptop orientation reading are:
- very high resolution (1920 x 1080 is a lifesaver and 1270x800 is barely tolerable)
- matte screen (gloss is pain in even under normal office lighting, not to mention in daylight)
For example the Sony F-series are decent as they can be bought with HD resolution and with matte displays:
http://www.cnet.com.au/sony-vaio-f-series-339305617.htm
Expensive? Unfortunately.
But the form factor for reading on a laptop is not very ideal for me as I prefer a portrait type display and not a landscape for most of my reading. Normal laptops just don't have this.
Then it's possible to go to a tabletpc, but they have much too low screen resolution and, imho, are too heavy to be handled like a book on your lap.