McGraw-Hill Education 20% Off Promo Code on SmartBook April 2024. SmartBook is a digital version of your course textbook. SmartBook is a subscription-based service. You can subscribe for 90 days, 180 days, 1 year, etc. You can access your book using laptop, tablet or smartphone and book is also accessible when you’re offline. McGraw-Hill Education (MHE) is a learning science company and one of the big three educational publishers. You can save up to 60% versus the cost of a new textbook. Promo code expires on 2/15/16.