I am typesetting a book and I have been asked to follow one book for design and the other book for all the display fonts. Can any one let me know what elements are included when you say "all display fonts".
Running text elements—Body Text, extracts, lists, and so on—(usually) use the same font family. Display elements can use the same font family as text elements but don't have to. Examples of display elements are the subtitle page, title page, part openers, chapter openers, front and end matter openers, heads within text, pull quotes, and can also include boxed text, tables, and figures if a font different from Body Text is used for them. In your case, they want you to use the running text elements' fonts and design from the first book, and any non-running-text elements' fonts from the second book.