Your benefits are determined based on your Books Per Acre (BPA) in each category. Quadrupling your BPA will generally double your bonuses.
Does that mean 1k BPA = double bonus? It goes by category or total?
For example, at 500 acres I need 500000 sci pts for 1k BPA. Does it mean 500k in alchemy = double bonus? Or once i have a total of 500k sci pts, every category will receive double bonus?