"In my garden I spend my days; in my library I spend my nights. My interests are divided between my geraniums and my books. With the flower I am in the present; with the book I am in the past. I go into my library, and all history unrolls before me." - Alexander Smith
Besides the wide selection of books (26 categories), the main reasons for the sale's popularity is that the books are priced to sell. In addition, the books are culled throughout the year by volunteers who discard damaged, highlighted and out-of-date books, making this one of the “cleanest” book sales around.
In total, we bought 10 books, all in fairly good condition and some even appear new. The books only cost us US$30, which is a real steal. For example, one particular book which I had wanted to get for a while would have cost at least S$50 in Singapore! 
We visited the sale on the first day (Saturday). On the third day (Monday), it is Half-Price Day and on the last day (Tuesday), it is Bag Day, during which patrons will be able to buy a plastic bag of books for $5. We would have gone back to buy more books, if not for the fact that we need t0 worry about how to ship them back. Also, "What refuge is there for the victim who is oppressed with the feeling that there are a thousand new books he ought to read, while life is only long enough for him to attempt a hundred?" (Oliver W.l Holmes, Sr.)
A little library, growing larger every year, is an honourable part of a man's history. It is a man's duty to have books. A library is not a luxury, but one of the necessaries of life - Henry Ward Beecher.