The tales chosen include A Midsummer Night's Dream, Macbeth, King Lear, Hamlet, Othello, and fifteen others. It is believed that Shakespeare wrote 37 plays so this is quite a nice selection.
The intent was to give the young girl or boy an idea of the plot or story of each play so that the reader, as his or her education progressed, would come to love the plays not only for the tale but for the language.
From their preface dated 1806:
The following Tales are meant to be submitted to the young reader as an introduction to the study of Shakespeare, for which purpose his words are used whenever it seemed possible to bring them in; and in whatever has been added to give them the regular form of a connected story, diligent care has been taken to select such words as might least interrupt the effect of the beautiful English tongue in which he wrote: therefore words introduced into our language since his time have been as far as possible avoided.
There is an explanation about the histories that...
For young ladies too, it has been the intention chiefly to write; because boys being generally permitted the use of their fathers' libraries at a much earlier age than girls are, they frequently have the best scenes of Shakespeare by heart, before their sisters are permitted to look into this manly book...
Well, there you have it. Two hundred years ago young girls and women did not normally have access to the plays of The Bard or many other books for that matter. Although, apparently Sister Mary did and how wonderful that she and her brother took on this project.
Wouldn't they be surprised today at The Tempest starring Helen Mirren as Prospera (not Prospero) which is the version I am going to watch.