I think it's easy to a data mining learner to work it out. But there are 2 points to be noted.
(1) only Apriori can be used;
(2) put forward ideas as many as possible, but feasible, i.e., can be used to recommend books to other users.
So, I wonders if the "Date" is useful and how to devise the transaction.
OMG, think more, stucking more, puzzled more.
