We initially used some engineered wood shelves, and they literally started sagging under our heavy book collection within just a few months. Before replacing them, I spent a rainy Sunday researching different brands and reading https://ebern-designs.pissedconsumer.com/review.html just to see how various materials hold up for other people over time. That research convinced me to finally invest in a hand-crafted, solid oak bookcase from a local family-owned shop.