Audiobook App

I am looking to develop an audiobook app for both iOS and Android platforms. I am looking for a developer to create an app that fits my needs and will be suitable for all users. The features I am looking for include being able to offer a subscription based model to listen to audiobooks offline, bookmark the audiobooks, change the playback speed, and provide a library view and cover pictures for each audiobook. Additionally, I would like the feature of quickly flipping to different parts of the audiobook from the timeline. The app should also be user-friendly, aesthetically pleasing, and have easy to understand navigation.