Who's Who in Shakespeare is a dictionary of all the characters from the plays of William Shakespeare. Literally. Every single character, bar none, even the characters who don't get actual names but things like "Courtiers" or "Soldiers".
Each entry gives detail on the characters, and in the cases of major characters, where Shakespeare might have gotten the ideas for just such a character. Such as in the entry on Tamora, Queen of the Goths from the play Titus Andronicus, the book tells us that just such a character sppeared in the works by the Roman writer Seneca, who apparently was admired by the Elizabethans.
The entries also discuss the lives of the real historical figures that Shakespeare used in his plays, and is filled with pictures and engravings of the actors and actresses who have played parts from Shakespeare. The first part of the book discusses both Shakespeare and his theatre, the Globe, and tells us that the listing of characters is from 36 plays, including all those published in the First Folio, and a play that was recently discovered to be a true play of Shakespeare, the Two Noblemen Kinsmen.
It also discusses the famous actors and actresses of the theatre through time, many of whom spent a greater part of their careers playing Shakespeare's plays. Some things do go undiscussed, perhaps because such information can be found elsewhere, such as the so-called "problem plays" of Shakespeare, which are plays that shift in tone between light-hearted comedy and dark and violent drama. They are sometimes called "Dark Comedies" and consist of "Measure for Measure", "Troilus and Cressida" and "All's Well That Ends Well". While "Measure for Measure and "All's Well..." end on a superficially happy note, the ending of the plays is not a satisfying ending and seems forced, while "Troilus and Cressida", purporting to be a Tragedy, ends without the death of the main character, the usual ending in such tragedies. Instead, another character, Hector, dies and the love between the two named characters is destroyed.
As you can see, this book will lead you to look up more on Shakespeare's plays. I read this book in between reading Edward Marston's Elizabethan theatre mysteries, and the juxtaposition of the books made me enjoy all three all the more.
While I can't recommend you go out and pick this book up for casual reading, because the kind of book it is doesn't lend itself to that. Instead, it's a valuable resource to anyone interested in the theatre or Shakespeare's plays.