In the previous two posts I talked about reader expectations for genre and story telling. Assuming you've met those criteria, then you need to determine how you are going to present that book in both printed and e-book form to meet those expectations. Now we get much more into formatting, page count, POD sizing, and all those geeky things.
Also, I won't be discussing e-book length because there is no "length" with an e-book. It is all dependent on the e-reader device size and the way the font sizing is configured. It is important, however, when completing the metadata for your e-book to fill out the information about number of pages (this is the number of pages the book would be printed). Because readers still use that as a gauge prior to purchase.
Traditionally, the mass market paperback
sizing used the formula of 250 words per page. With the typical double-spaced manuscript using Courier 12pt font, that means that 85,000
words would yield a finished book of about 340 pages. If you are self-publishing and writing
at that length I would definitely suggest using the 6 x 9 inch format. You
want to keep your print costs as low as possible in order to
competitively price the book. At 6 x 9, using a TNR 12 pt. font the
formula is about 350-400 words per page depending on the leading (space
between lines). So, that makes an 85,000 word book come out somewhere between 214 and 244
pages. Significantly different from the 340 pages using the traditional MMP formula and a savings of about $1.00 per book in printing cost.
What Impacts Printed Page Count?
Physical book size. The page count has everything to do with the format size (Trade paperback sizes are typically (in inches) at 5.25 x 8 or 5.5 x 8 or 6 x 9). The difference of 1/2 inch or one inch can be the difference of 50-100 pages in a book.
Line spacing (single, 1.5) also makes a difference. Taking your manuscript from the usual double-spaced lines to single-spaced cut it in half. Most authors select 1.5 spacing, but others might make it slightly less or slightly more depending on their need to limit or expand page count. If you use a great page formatting software, like InDesign, you can effect this line spacing significantly with what is called leading. You can tweak a line to be slightly more space or less space than the line before it in order to control page breaks completely.
Fonts. Any user of a word processor knows that all fonts are not alike. A 12pt font in Times Roman is a very different size from a 12pt font in Garamond or Courier. The fonts you elect to use for headers, subheaders, chapter numbers, quotes, etc. are all variables you can manipulate and will make a significant difference in the number of pages. I've helped an author with a very long book, cut out 50 pages by simply changing the header font from 18 pt to 14 pt.
Blank Pages. Traditional book publishing designed book interiors so that new chapters always began on the right hand side of the book. (the odd page number). This means if your previous chapter ended on an odd page number, that a blank page would be placed following that chapter end (the backside of the chapter page) in order to have the next chapter open on the right hand side. Depending on the number of chapters you write, these additional blank pages can be significant. For example, someone who writes many short chapters (say 50 chapters) could easily gain 25 or more pages in the book. The elimination of these blank pages, either by not using them or by deleting content to make sure they don't exist, can make a significant difference in overall page count.
Front and Back Matter. Word count of your completed story is not the only thing that impacts overall page count. Beyond your story, a book has front and back
matter (e.g., title page, copyright page, dedication,
acknowledgements, excerpt for another book, request to join mailing
list, list of other books by the author, etc.). I usually figure 0-15 extra
pages for this stuff.
Why Would I Want to Change Any of These Parameters?
For example, in the genre expectations section you learned that reader's expect a longer book for Historical Fiction or Historical Romance. What if your book came in at 70,000 words and the expectation is 85,0000 to 100,000? You can still make the book "feel" longer by choosing a smaller physical book size, or making the font larger (go from 12 pt to 14 pt), or adding more interest to your headers, or making sure you use the right hand chapter openings and add those blank pages. You can also add more back matter, such as a longer excerpt of the next book.
As with all perceptions of value, you want to present a product that meets expectations of look, feel, and size to get the reader to try the book. However, the choices you make also build an expectation (a promise) of the reading experience. Because reader trends are to look for shorter books, having a longer book carries a burden that is more difficult to meet. Presenting a longer book tells the reader that the experience is going to be worth the additional time and money. If you don't deliver, the reader will be likely be more upset than if the book didn't cost as much or take as long to read.
Of course, these are generalities. Every book, every genre, and every reader combines to create a unique experience. No book can meet every reader's expectations. Obsessing over making sure your book is perfect in every detail leads to madness. You can only write the best book you can, get it edited by the best editor you can afford, and then package it in a way that meets genre and reader expectations as best you can. Then let it loose in the world and write the next book.