Sentence:  But why did very good players shy away from cards that are so obviously good from our perspectives? One very real possibility is that <WSD>library</WSD> manipulation/increased selection and redundancy tech had not yet been established - after all, many players were amazed at Lestree's use of the Sylvan Library to draw extra cards! 
Meaning of the word marked with <WSD> tags:  The deck or draw pile.