I LOVE American Girl dolls and their products as an adult collector
The Beforever line is the new name of the historical dolls. A few dolls have come and gone over the past few years, though you can still buy the retired dolls books, but they probably have not been updated.
The original historical girls were:
Samantha (who retired and then returned) 1904
Molly (who is currently retired) 1944
Kirsten (also retired) Pioneer times
Felicity (retired) - Revolutionary times
Also the historical dolls include:
Josefina - 1824
Addy - Civil War
Kaya - Native American
Kit - 1930s
Julie - 1970s
Caroline - 1812 -- was a newer doll that didn't sell well so retired
Marie Grace and Ceceile - 1853 times -- newer dolls that also did not sell well so they retired
Then the newest doll that just came out is
Mary Ellen Larken from the 1950s and as someone already said there is a new girl coming this summer for the 1960s.
I personally LOVE the historical line. They did change up the format of the books when they rebranded the line. In the past they had a series of 5-6 books for each historical character. I have not actually seen any of the newer books in person but I understand they took the 'original' stories and put them into two larger compilations for each of the current dolls still for sale and then they added a new story about a girl of the present going back to the past.
I believe the mysteries and short stories are just additional stories about the girls. I've heard they are very engaging, but the main compilations would introduce the historical girls better with their stories.
Love, Love, Love the collections
So if you need more suggestions just let me know