The Kindle suits me. The power supply is good enough to cope with a week long festival without recharging; I have a case for it which has a built in light if I need it; small but big enough for most purposes, and fits into a - large - pocket in my jacket. Lots of things it can't do, of course, but as a device to carry round books, including song books, it fits the bill, and is much cheaper than the iPad variants.