On a page over 6 inches wide, text lines are generally too long for comfortable reading in a single column. Typesetting guidelines suggest an optimal line length is between 1.5 and 2 alphabets (39-52 characters). The standard letter format with 1″ margins on a 8.5″x11″ page is too long. Do your readers a favour and consider line length along with font choice for ease of reading.
Columns can work. Three columns are generally more appealing than two, but line length may too short, so still not be optimal. A wide column for text and a narrower one for notes and tips or other design tricks can keep your wider book from looked too staid. If you don’t need the page size for graphics, consider a smaller sized book.
Open pages are inviting. Print a copy of your intended design to see how it actually feels. Indents, line and paragraph spacing should reflect the tone and invite the reader to stay a while.
Long paragraphs will appear as a wall of text. Lean towards journalism and break up longer paragraphs. You have pulled together great content, don’t let poor readability be a deterrent.