I was disappointed in this book, having enjoyed blackwork for a number of years I thought an essential guide from the RSN would be something really worth having. However, there are only 37 diaper patterns in this book and I already have a bigger collection garnered from other authors, the requirements list is, to me, far too complex and off putting for anyone looking to start this fascinating embroidery and there are better books than this if you are a beginner. If you want to progress to designing, then the sections on design and shading are probably useful but much of it can be found elsewhere. It says it is an 'Essential Stitch Guide' so no projects of course, but with so few stitch patterns (the basis of blackwork)it really isn't very essential either. Do I buy the other Essential Guides due to be publiched? On the evidence of this one the answer is 'No'.
As an afterthought - in the history it is stated that this technique was popularised during the reign of Henry VIII and is generally thoguht to have been introduced by Catherine of Aragon (1509-1533). Most embroidery historians I have read accept that she popularised it but think it is mentioned much earlier in Chaucers Canterbury Tales (late 14th century). Important if you want accuracy.