Not nearly as useful as it could be, this is a sort of cheat sheet for people who attend Renaissance fairs. It is of no use at all for anyone with a serious interest in history or authenticity. It gives very general advice on how to construct costumes, with hand-drawn sketches which illustrate in a general way how to do things. There are no real patterns, nor are there any actual original images, just the author's sketches. If one doesn't already have quite advanced pattern drafting and sewing skills the book will be frustrating and baffling. If one does, one hardly needs this book.
If you need cheap, down and dirty costumes for Halloween, this is the book. If you want really Elizabethan clothing patterns and history, start with Patterns of Fashion by Janet Arnold.
While a lot of the research in this book has since been superseded, everyone has to start somewhere and you could do worse than this book.
It's pretty useful in helping you understand how various pattern pieces and garment shapes go together, as well as a quick overview of clothing styles of the period. But then you should really move on to more more solidly-researched stuff.