Kobo Ereaders

[Tarser]

I have a mini Kobo. I am thinking of getting a bigger Kobo with a light, or even a Kobo tablet, keeping the mini for when I'm out and about, always in my pocket for when I've got a spare moment. If I get another Kobo, will I be able to have all my books on both devices so that I can read from one whilst having the other one automatically updated. I've read somewhere that this is possible but is it complicated? I'm not much of a 'techno'. I don't know what an 'app' is except that it's short for 'application' . Any opinions on what sort of kobo is best to get? Thanks.