There is no such thing as a 'best' font or size. Different publishers have their own standards, which can entail the use of different fonts for headings, body text, footnotes, captions, etc, and these and the point sizes can vary according to the publication format. If you like the font and point size in your link, simply find one that matches/approximates it.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Probably I can match the font by looking in the book.

How do I match font size? Trial and error? Count the words in 10 lines to see if they match?

How about the margins? 1/2"?

The book will be published as is in the Word document.

Wider margins are best because they leave room for notes. Also a shorter reading line makes it easier to read. Many text books split text into columns to shorten the lines of text.

A general rule is to use serif fonts for body text and sans serif fonts for headings.

The serifs are supposed to make it easier to follow a line of text.