Let me tell you if you are not used to the length of long movies or long TV series don't even start this one.
The episodes are 2 hours minimum with half of it extended to 2 and a half hours. The Turkish are known for making long series.
It tells the story of Kosem Sultan (true story actually), and her reign over her husband Sultan Ahmed I, her two sons Murad IV & Ibrahim I and her grandson Mehmed IV this three last people she was a regent during their reign for half of the time at least.
The historic facts are good with some characters being changed in some fiction whereas the facts are different. But very little to minor characters. This is a continuation of Magnificent Century consisted of Sultan Suleiman and his reign.
It's good some plot holes and some things not right but overall they did a good job considering the length and the huge amount of material they had to put in, in so little time and less seasons otherwise telling the whole story it would need probably 20 seasons.
It tells the story behind the gates of the palace, in the harem where women manipulate and are powerful of their husbands with great positions , even an Imperial one. The actresses portraying Kosem change but overall they did a good job, each one of them on itself.