This horrible, horrible visual novel made be cry! As its intention was evoking emotions, it did the job.
Let's get down to business (I will keep this spoiler-free). Narcissu visual novels (VN) are not strictly games: they have no interactive parts whatsoever. You can just click away and the story continues linearly with no choices. Even the achievements are just reading the novels to their ends.
Narcissu (both of them) is a story about people living with
a terminal disease. Note the emphasis. It's a highly emotional and tragic story, with death being a constant theme. Nevertheless, the characters lives are what's important.
Curiously, the type of the disease is left unrevealed in all cases, emphasising the life of the person instead of the sickness. At all times the story follows one of the protagonists from their perspective, revealing what goes through their head. (Most) Protagonists and some important characters have voice-overs for their dialogue. Scenes are covered by nice, melodical piano songs and occasional other instruments.
Apart from many other visual novels, the visuals are very simple: usually there's just a serene scene that depicts the place where the events take place e.g. a kitchen or a countryside. There are very few scenes with people. The style didn't appeal to me strongly. However, I think that at important (i.e. dramatic) times the scenes were well done.
A couple of things about 1st and 2nd novels separately. In my opinion Narcissu 1st begins slowly, with the protagonist being admitted to a hospital and angsting away there. In Chapter 1 it seems like nothing is happening and frankly I was bored while reading it. Fortunately, in half-way through Chapter 2 it finally begins happening, so be sure to endure until that time. Narcissu 2nd is better in this respect as it has a branching story line from the beginning with several characters.
While both VNs are originally Japanese, there are fortunately two English translations of Narcissu 1st. The Agilis translation (the one I read thoroughly) has rather lot of typos and in some small parts it is left unfinished. To me it felt rather clunky. Only afterwards I briefly checked the gp32 translation and it turns out gp32 is a more polished and "proper" translation to English than Agilis. Narcissu 2nd has only Agilis translation to English that was fortunately a lot better and more polished than the one in Narcissu 1st.
For me, Narcissu 1st was 3-hour read and 2nd a 5-hour one. While it's possible to skip through the story by pressing CTRL for achievements, I can recommend reading through the story: it's an emotional and even revealing experience to issues and thoughts of people suffering from difficult diseases. As such, it provokes one to think about life perhaps from a new perspective. To me, that makes it worthwhile a read.