An electronic device includes a stack assembly and a cover glass. The stack assembly includes an electronic paper display sub-assembly for rendering content, a front light sub-assembly for illuminating the electronic display sub-assembly, and a capacitive touch sensing sub-assembly for detecting touch inputs. The cover glass includes two apertures for the placement of control buttons for the electronic device. Prior to assembly of the electronic device, the cover glass is strengthened after the two apertures are formed so as to strengthen the interior edges of the apertures.