You can easily put the titles onto your Kindle, by plugging your Kindle into your computer, opening it up like a disk drive and dropping in the files into the 'documents' folder.
There are lots of different titles available, but the copyright is a bit dodgy unless the books are classics and out of date. There are lots of really good selections of books - but they are unlikely to be legitimate. Plus, although some can be fine (my sister had a disk and brought it round to show me) - there are lots of others that have naff formatting.
I got one of about 250,000 books for about £10 on cds. You have to unpack the books as they're all compressed, and download Calibre. Once you've got Calibre, you can export the books from the pc to the e-reader.
There are loads of readable books on it, but can't remember how many children's books. Why not ask the seller?
Ah. Not seen those. Again you'd need to check they could be downloaded to the nook. My understanding is that it's less restrictive in terms of where you can download from than kindle which is tied into amazon.
It may or may not bother you but I'd also be asking the question over whether they were legit. There's a lot of pirated stuff on eBay too.
Are they worth it? Just brought my dd one of those cheap Nooks and want to get a load of books for it. I've seen those cheap cds with 1000 books for £3 - are they just trash? She's 7 so am after childrens books. I saw one that was all the famous five books for £5 - which almost seemed too good a deal - how do I know which are legit or not?