Here are more (dangerous) websites where you can find previews for art related books.
And there's also Creative Uncut's gallery, which features the art but not books.
If you know of others, share them via the comments.
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Other useful links

My online alias is Parka and I'm a Singaporean dude.
On this blog you'll see art related stuff, reviews of art books that I read and collect.
Most of my reviews appear on Amazon. If you find them reviews helpful, throw me a vote on Amazon. Thanks for the support!
You can reach me at 
Review an art book and win prizes.
Buying from these links helps support Parka Blogs, fund contests and giveaways.
Comments
Hi Parka, My new website, Art
Chia Huei (not verified)
January 2, 2010,
34 weeks 5 days ago
Comment id: 1188
Hi Parka,
My new website, Art Books Reviewed (http://www.artbooksreviewed.com) provides previews of books on learning to sketch and paint. It's still a small website but I am trying to grow it over time :)
Thanks for all your previews and reviews! They have been very helpful for an online shopper like me.
I was going to recommend
nysv (not verified)
January 2, 2010,
34 weeks 5 days ago
Comment id: 1189
I was going to recommend CQコミックスタジオ, but I see you already knew about it!
There's some interesting stuff there - for example, I had no idea they had actual enviroment photo reference books in Japan for comic artists. Pretty cool stuff, I'm a sucker for good reference material.
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