This is an excellent PUBLISHED BOOK.
Harvard is a "style" therefore each university produces its own version of Harvard. Most lecturers (but not all) have not kept up to date with new media, this book solves this problem. Sources in the UK have been "secret" course handbooks from YOUR University which is fine as long as you do not change university or the university decides to change it as part of internal power politics, without telling the students (true story). Many very good online pdfs are available but are from "academically unacceptable" sites or are "American".
In case you do not know, Harvard is in the United States of America, this may possibly be an explaination. However, as I have not correctly referenced this wild statement from an academic source it is obviously wrong.
Because this is a published BOOK from an academic institution, in the UK which has gone through an editing and publication process; it now becomes very difficult for lecturers to bully students about their referencing. It is either right or wrong according to a published book standard, not a subjective standard created in one academics head to suit their university agendas.
This book helps in the national UK standardisation of the Harvard Style. However, its main advantage is it is: modern; off the shelf and cheap. I raise my hat to City of Sunderland College for solving a problem which has existed for three hundred years within the university system due to non-publication.