There are many general books on family history research, most of which have a chapter on wills, but this book covers the topic in detail. It is comprehensive and would be a welcome addition to the bookshelf of the more advanced family history researcher.
I feel there are two areas in which the author makes generalisations, where further clarification could have been helpful. Firstly, he states that in the past, people tended to make wills when near death, the implication being that they died shortly afterwards. That is certainly true in the majority of cases, but there are others where an elderly testator must have made his or her will when suffering from an illness from which they subsequently recovered, or which lingered on for several years before death, and it is not uncommon to find examples of wills written up to 5 years before death, and occasionally earlier. Secondly, the author states that the range of kin named in wills did not generally go much beyond the nuclear family. That is certainly true, but not all testators had a nuclear family as such. Elderly bachelors, spinsters and childless widows and widowers would often have a large number of nephews, nieces, great nephews and great nieces, and leave bequests to all of them. Relationships were usually specified and the surnames of married nieces and great nieces given, so a will written by such a person can be a genealogical goldmine. Such a will can provide the tools to break down an otherwise unsurmountable 'brick wall' and I am surprised that the author did not point this out, or give an example.
There is a misprint on page 51: Doncaster, Co Durham, should be Darlington, Co Durham.