Thanks, guys. Yes, it's dull and wintry here in the UK, so the light isn't that great. Plus, the room I work in is out of direct sunlight for much of the day. Next time the sun shines [if ever! LOL] I will take the 505 out into the garden and see how bright it looks.
In the meantime, I've got a lighted cover and also a Mighty Bright Xtra Flex 2. The lighted cover isn't perfect, but as I saw in a couple of other threads here, that's pretty normal. The Mighty Bright makes the 505 really nice and bright though. I think I'll keep the lighted cover for when I'm out and about, because it's not as noticeable and it's handy, but use the Mighty Bright for reading in the evenings at home.
Now that I know my 505 is okay, I've installed the software and downloaded my first epub ebook! First of many, I guess...
Thanks again for the feedback.