A drug encyclopedia, my favorite. The Essential Guide to Prescription Drugs is one of the most detailed and easily the most usable of the breed. It contains in-depth listings of the 200+ most frequently prescribed drugs, complete with mode of action, side effects, contraindications, time required for benefit, recommended follow-up exams, interactions with other drugs, and —especially hard to find—use during pregnancy and breastfeeding. No opinions or recommendations here, just the facts.