It depends. I do buy from Amazon quite often, but I'm also just as likely to buy books in my local indie store (that I've been going to faithfully since I was 7 years old), or chain stores like Borders or Barnes & Noble. This afternoon I spent about an hour in my local used book shop. (I could have stayed much, much longer, but it was snowing here and the roads were starting to look pretty treacherous.)
Price-wise, Amazon is great. Service-wise, it doesn't get any better than my local independent. For convenience, Amazon and Borders (the closest brick and mortar bookstore in my area) win out.
I buy mine from Amazon. It's hard to get into & out of a physical location with two little kiddos in tow. I've made trips down to Portland in the past to shop at Powell's, which is like book heaven, because it fills a whole city block, is four stories tall, and has more than a million books! I also get books from PaperBack Swap.
I don't buy many books. I usually take them from the library. When I do buy books, I often go to The Strand in Manhattan, New York because they have very nice discounts. Their online store is very good as well. I sometimes go to Forbidden Planet as well.
I only buy from a chain store when someone gives me a gift certificate. Otherwise I buy from a local used or independent bookstore. Instead of looking for a particular book, I just look for interesting books that they have. This has led me to some really cool finds that I would never have encountered on Amazon or in a chain bookstore.
Looks like you guys are all thinking cheapest place to buy books. I personally like ambiance of a large bookstore where I can actually feel and touch the bound volumes as I scan titles or pick up and read bookcovers to get a feel for the book. So, I have to say a place like Barnes and Nobles is where I mostly buy my books.
My most recent book purchase was from the local independent book store. I like browsing and buying books in person.Online, I have never purchased a book from Amazon.com, and I like purchasing directly from the author's site or from the publisher. Another favourite is independent online book stores. For business books, I highly recommend the indie 800-CEO-READ.
I am also a heavy buyer of used books from used book stores, thrift shops, and garage sales.
There is no independent bookstore nearby, and while I enjoy hanging around the Big Chain Bookstore that is fairly close, I have found the selection is rather limited. If it is a popular book or a well known classic and I need it right away...or I have a lovely gift card..well, yes, I will most likely look there. And like I said, it is a nice way to waste an afternoon, looking around.
But 95% of the time, for selection, convenience and price, I go to Amazon, for new or used.
You all might try purchasing direct from the author whenever possible.. Especially from us little knowns, The real issue is supporting the author not Amazon or B&N. The fact is, if you purchase from the book stores you will pay about the same (probably more) and the author gets a fraction of the revenue. If you buy from the author, then the creator will get a much better deal. Example: my book ZAHIR sells for $11.95 per my contract with Amazon and B&N. If sold through them I make about 11 cents per book. If I sell though my website, I make about $2.50. My 2 cents, LOL.