Amazon on Wednesday pulled the wraps off a new premium e-reader that’s waterproof and has a sharp 300 pixels-per-inch display. The Kindle Oasis has a 7-inch Paperwhite display and sports an aluminum back and ergonomic shape that makes it easier to read for prolonged periods. It has a battery life measured in weeks, and it can charge from zero to full power in two hours. Audible, Amazon’s audiobooks service, is built into Oasis. Its base price is $250, and it will begin shipping on Oct. 31.