I strongly dislike the CHM format. The reason is that it is difficult to study from CHM files. You simply cannot highlight or annotate CHM files. Nor can you refer to a specific page. And there aren't many good CHM readers on iOS compared to PDF readers. This is why I prefer converting them to other formats such as the PDF format and ePUB format. This app does a really good conversion to the PDF format. I think it did the best job of all the other CHM readers. It even retained the table of contents - which others fail to do since they all just use OS X's print function to get their PDFs. This app does a smarter job. This app completely FAILS to convert to ePub format. In fact, it crashes when you attempt to do so. This is why this app receives 3 stars. It fails to do ePUB conversion. And ePUB conversion is what you have to buy extra through an in-app purchase. When it is updated so it can do an ePUB conversion, I will then update this app to 5 stars. It shouldn't be so difficult. Both CHM and ePUB are essentially HTML-based files.