What is this from(A book called Flowers obviously) and where can I find it.
It's an excellent series of yuri visual novels, made by Innocent Grey.
There are four parts, named after seasons (printemps, ete, automne and hiver), and they are sequels to each other, even though the main pair regarding romance varies. Last novel was translated frequently, and you can buy all of them from Steam, for example.
Flowers goes about its thing by continuously depicting a whole school year in a rather isolated Catholic girls school, while also featuring separate romantic storyline for each season.
Out of all yuri novels that have ever been made, these are some of the highest quality ones, right up there with Kindred Spirits. Art is notably excellent. They're not particularly lewd, but they are passionate in terms of romance and the story is not shy to portray sexual attraction, when it fits. There is little bit of mystery, and lot of slice of life type situations.