Well, today I have a few things to say, or lists to suggest you view:
Firstly here's a wonderful list of the top 50 children's books, as voted for by Australian kids. Harry Potter seems to be a favourite and it's useful to know just what kids like if you're aiming at them, even if they're Australian!! The Red House Children's awards are a similar list in Britain, voted for by kids.
You may well know that at the moment the Carnegie Awards are being decided and I've always found these to be great indications of really good novels for kids.
As for adult reads, well here's the New York Times bestseller list and if you go to Amazon, they have a Hot 100 list for almost every kind of product available. Here's the one for books
Another useful list is Ottakars top 10 . I love this book shop, although it may well be taken over by the HMV group and become part of Waterstones from what I've read. Still, you can see what's selling.
I think being aware of what sells is crucial when you are writing, especially if you want to make a living out of it.
Of course, you need to write what you feel passionately about, but at the same time knowing whether it's likely to sell is a must.
A.S Byatt obviously thinks bookshops are biased against good reads, in favour of best sellers. Well, at least she did in 2002. If you've read Possession, her Booker prize winning novel, which I tried very hard to do, you may well understand which category her novel might fall in to! Now, that's a literary monster of a novel. Definitely not an easy read.