I understand that the name of "Oxford" itself should demand trust for this book, but there aren't any citations and sources in this book aside from a list of "further readings". Is this book trustworthy as secondary source?
Usually the Oxford [or insert large UPress, Cambridge for instance does the same thing] History of [insert topic] are pretty good.
They are often overviews of a field, sort of a marker for where the field is at a particular point in time. If you ever have doubts, go ahead and google the lead editor on the volume and see who they are; they should typically be someone near the top of the field.
Looking up this particular book; looks to be more in line with a textbook offering. Textbooks often avoid heavy or lengthy citations, but are still good markers for where a field is at a particular time. The synthesis involved in writing a textbook is an art unto itself.