I think you're all being waaay too paranoid.

Getting a really nice A1000 is no mean feat these days, it'd cost a lot to get one good enough for a book.
Secondly, if he wanted it for a scam like on eBay then he'd just get one
off eBay wouldn't he?
If he's writing a book then when he says "high-resolution" he means it! In other words, not compressed JPGs or anything, but full resolution TIFs which are large and completely unsuitable for eBay and the like. Also he may not know about any other Amiga sites!
I don't see he's got anything to gain at all by asking unless he's genuine, I
severely doubt he's anything other than a kosher bloke trying to get the best quality pics for his book.