I use Verbum both on my iPad, iPhone and MacBook Pro. There is a free app for the iPhone and iPad, but you can also pay for additional resources depending on your needs. I especially like the ability to create reading lists like reading the Catechism of the a Catholic Church in a year, or reading the RSV Catholic Edition of the Bible in a year. All the versions give you the ability to notate and highlight or even create lists of notes that deal with apologetics, areas for further research, notes for papers, etc. All of the resources (bible translations, commentaries, council documents, writings of the early Church Fathers, etc.) are all interlinked so that when you are reading in the writings Saint Justin Martyr where he is describing the Holy Mass as it was being celebrated by the early Church in 155AD, there are links and references to the scripture that He quotes, other Church Fathers and other resources. The system is constantly being improved. There is even the ability for Priests or Deacons to use the system to help them create and research their homilies. The Verbum system is completely Catholic which is great and there is an ever growing library of resources to help grow in our beautiful faith. The system really sings when you open it on an actual laptop or desktop since that was what is was designed to take advantage of however it is also the best bible study app I have ever used on my phone or tablet. I tried many of the versions mentioned previously in this thread and while some of them had good qualities and aspects, they did not have the depth and functionality that Verbum offers. The only thing that is missing is the incense.