Marvin will continue being developed, updated and supported. Nothing really changes here. In fact, just yesterday, Marvin got it's iPhone 6/6+ update.
Re Gerty: I like the concept of a reading journal very, very much and use it daily. I also wanted to give the idea of a more causal ebook reader based on vertical scrolling (but still more powerful than others) a shot. Many people find Marvin complex and I wanted to see if I could do better for them.
In a word, it's about choice. I've also made the vast majority Gerty's reading and journalling capabilities free for anyone to use and see if they like it. A single, one time in-app purchase unlocks all the remaining features and helps support the development of Marvin, Gerty and some new apps I have planned for later this year.
People who prefer using Marvin as a reader can use Gerty as a journal only. In fact, Gerty is designed to also let you catalog your paper/eink/magazines/kindle books too to journal against them (it also has a barcode scanner). I'll publish URL schemes soon as well as include Gerty's journaling features as custom commands in Marvin very soon.
I've put Gerty's feature list on
appstafarian.com together with a trailer. I also wrote a quick "
getting started" guide that addresses many questions people are asking.