TotalReader Pro is a digital reader for iPhones and iPads. It costs $4.99, but it was free the day I downloaded it. It reads books and documents in all the common formats, such as .docx, .epub, .rtf., .doc, .ppt., .pptx, and many more. I have tried it and it works well, better than the other e Readers I have on my iPad. You can read about it here:
It has also made iTunes U its learning management system.