Also, are some of the templates better than others for a relatively large book that will be 50% text?
None of the predefined templates is really suitable for books with large amounts of text; the "journal" theme has pages with larger text blocks. The "Photo Essay" theme will give you also pages with only text.
You may need to define a "custom" theme for you specific layout.
Is there any editing function within the Aperture photobook program that allows me to edit the format of text, other than to change the fonts?
The "Edit > Show Fonts" panel (in "Edit Content" View) is the only one I could find. But it lets you control all aspects of the Text, size, spacing, alignment, centering. Have you tried these options?
Sorry, I never tried to paste Word Text into Aperture Books.
Finally, if I can be so bold as to ask within this community, are there other on-line publishers that are more suited to this task?
Have a look at the Aperture plug-ins for third-party books: http://www.apple.com/aperture/resources/third-party-books.html
I have not tried them, but they seem all to produce very high quality books, but the description is more concerned with the elegant binding and cover than with the page layout.
One question: Do you want to create a printed version of your book or do you want to create an ebook? If it is mainly for onine viewing or for creating a pdf-version, you might prefer to create the book in iBook Author. That has much more advanced layout options for Books with text.
If you are having trouble with formatting text pasted from Word, try pasting it using "Edit➞Paste and Match Style" (if it is available -- I can't check right now). (The shortcut is "⌘⇧⌥v".) Then use only the Aperture Book text formatting tools for formatting text in Aperture books.
Alternatively use Text Edit to write, after setting the Text Edit document to Plain Text (on the Format menu).