A number of researches have been conducted to improve the accessibility of various types of images on the web (e.g., photos and artworks) for people with visual impairments. However, little has been studied on making comics accessible. As a formative study, we first conducted an online survey with 68 participants who are blind or have low vision. Based on their prior experiences with audio-books and eBooks, we propose AccessComics, an accessible digital comic book reader for people with visual impairments. An interview study and prototype evaluation with eight participants with visual impairments revealed implications that can further improve the accessibility of comic books for people with visual impairments. The results showed that the participants' preferred features of the prototype, audiobook and eBook.