The price groups of these lists are designed to aid librarians in adjusting their purchases to definite budgets for science books. As before, these price groups indicate our judgment as to first purchases that will secure both quality and variety; $10 buys our choice of key books; $15 more adds our next recommendation to complete the $25 list; $25 more supplies a practical $50 list; $50 more swells the order to a $100 list; $150 more presents a really comprehensive $250 list; further titles provided for alternate choice, or for the grand gesture of spending nearly $500 in a single year for science books on the high school level.