I recommend this book for those who enjoy reading British literature from the 16th and 17th centuries not just Shakespeare.
That being said, The Bedford Companion is less about The Bard, and more so about the times in which he lived. While attention is given to his plays, equal attention is given to such things as the history of the Globe Theater, Shakespeare's early life, the economic situations of the time, and a history of Shakespeare appreciation, or "Bardolatry". It shows Shakespeare as a human, as a buisinessman, a family man, and how he eventually become know as the greatest writer in the English language. (Most of his plays weren't published until after his death.) This book may not help you fully understand Hamlet, but it can certainly make it more interesting.