It's weird- I also downloaded about eight or so of the above listed books for free two days ago.
After a quick check, one,
The Rule of Three is not listed as being $0.00, neither in a 'searched for' list nor when you actually click the book. However, another book,
How to Be Good is listed as $0.00 when you click to see the book's listing, though it has an actual price when in the 'searched for' list.
All I did to find the books was use the search box in the top right of the CONNECT software and find them by their titles. I guess Sony did mess up a little in offering at least some of these books for free....