I really like the books of LM Montgomery. They are often regarded as childrens' or young-girls' books, but they reach well beyond their genre, and they are very funny and wise.
By far the darkest one is
Rilla of Ingleside, because it relates to WW1.
In it, one character comments to another about the past two years which have been very difficult. And she asks her if she would exchange them for two years of happy times. And the other character said that she would not, because of how much she has changed and grown.
But they agree that they would not have the heart to ask for two more similarly hard years, and the older character says how it's remarkable that
even if and when we recognize how hardship has made us grown, we never want more of that kind of medicine, which is why we are not ourselves in charge of our path.
I thought that exceptionally wise.
The first book in the loosely-connected series by the way is the famous
Anne of Green Gables. I think Lucy Maud Montgomery did a fantastic job in making a series of books taking place through the life of Anne Shirley, and have them all fit but yet be independent. Some of them don't even have Anne as main character, which is true of
Rilla (Anne's daughter), and
Rainbow Valley, one of my favorites, which is about two sets of siblings. The most important set of siblings is not even in Anne's family, but the book still fits perfectly in the whole saga.
The books are pretty much independent, but I think one may find greater satisfaction by reading them in
sequence.
Almost all of them can be found on paper, ebook, and audiobook. (Though I haven't been able to find the sixth one,
Anne Of Ingleside, in audio. If anybody knows of it...)