You should be able to make a Connect Four AI that is sufficiently effective without any use of opening books. Unlike say, chess, there are very few openings and no considerations to be made for openings that might lead to bad positions in a dozen moves or more, other than your program should definitely play a central stone on its first turn (if it goes first). That is assuming you're doing a standard 7 x 6 board.
I couldn't disagree with you more. The first few moves in connect 4 can be very counterintuitive and an opening book is essential.
EDIT: Let's number the columns 1 through 7. Take 2-ply position after the first player plays 4 and the second player plays 1. What should player 4 play next? There is only one winning move!
The way you use John's database is quite simple: Write a minimax searcher that treats 8-ply positions as leaves and uses the values from the database at those nodes.
Edited by Álvaro, 20 June 2014 - 09:29 AM.