Ren'py is quite user friendly at first. You don't need any prior knowledge in programming to create a linear game with a few crossroads. The bottleneck will always be the creation of new CG. And when you want to create more than just a slideshow, Ren'py (python) gives you the opportunity to write complex scripts (e.g. Our Red String, Seeds of Chaos, Bright Past).
Since Ren'py is open source and the file structure across all games sameish, it's quite easy to copy other people's code to give you a better understanding of how it all works without reinventing the wheel.
I personally don't understand why anyone would start with Unity. It hogs needlessly resources even when the games are not more than glorified powerpoint presentations. The Spellbook, Mad Turn, My Wife's a Star - they would all have benefited from a slimmer UI.