I've been looking for an ebook and PDF reader which allows for bookmarking, and the synchronization of these bookmarks on my Android KitKat smartphone. The ability to have a black background (for ebooks) is preferred but not necessary.
After uploading your files, you can enjoy reading them with all the nice features available: bookmarks, highlights and notes, dictionary and more. What’s more, your reading progress, highlights etc are synced to the cloud, so if you have multiple devices, you can easily pick up reading anywhere!
Also, in Google Play Books for Android's settings, you can change the theme to "Night" in order to give you a black background.