Slate is a great roofing material for many reasons: it is strong, durable, and waterproof meaning that it isn't vulnerable to rot as other shingles can be. Slate also offers good fire protection and comes in many shapes and colors.
The downside of slate shingles is that they are expensive and labor intensive to install. However, slate roofs are some of the most durable and long-lasting. So even though slate seems expensive early on, it can be a cost-effective option in the long run.