Third option ... keep the bookcases below grade. My bottom floor is underground, so only light entering is through two window wells 5 feet deep and 20 feet away; no chance of direct sunlight. Ever!Jerome's example is a good one. There are a lot of options that all have varying levels of quality, UV protection, visibility, and price. You may want to search for local professionals that install the glass coatings and discuss options and costs to have it done professionally. You may choose to do the windows in the room. You may choose to do the windows of the bookcases. Or both.