The simple way to load an audiobook onto an iPhone is to use a drag-and-drop substitute for iTunes, like Copy Trans, and then use an audiobook player app. from the Apple store to play the files. Jump ahead to step 11 for those solutions. What follows below through step 10 describes how I made the effort work using iTunes, but only for a time.
I had been trying for months to load an audiobook in MP3 to my iPhone 4S. If I was able to load the files, they did not stay in their proper order.* I looked for help in Apple support documents and in articles on the Internet; but those I found were for earlier versions of iTunes and not helpful or they were too general and did not cover the problems I was having. Many people seem to have frustrating experiences with iTunes, especially when trying to add an audiobook to an iPhone. Finally, I got it to work and I want to document the steps I used. I hope this helps anyone who has been struggling with this. (Update: I now have an iPhone 5C. Everything was going well with my audiobook [a Bible in a 2nd language: German] on my iPhone, but it suddenly ceased holding my place. See step 12. I got an app. for playing an audiobook, and it works well.)
I am using iTunes 11 with Windows 7. The audiobook I have been trying to load is the 1964 edition of Luther's German Bible. I got it from SERMON online: Die Predigt Datenbank. The files are MP3. I added alpha-numeric coding to the names to keep all 1,189 files in their proper order.** For demonstration purposes in this Instructable, I will use audio files for the World English Bible from Audio Treasure.*** Both of these versions may be copied without copyright infringement. (The World English Bible is a slight update of the American Standard Version of 1901 to make the language more in keeping with today's English.)
I like the German audio Bible because it offers me an opportunity to practice my German. However, many who read this might be more interested in an English version, whether the free World English Bible or a paid version of your choice. You may also want to load other audiobooks onto your iPhone. Audible has audiobooks available for the iPhone through a special app., but, there is a subscription price and I could not find any German Bibles.
* As noted in the second paragraph, the audiobook is a German Bible in audio. Genesis 10 would play immediately after Genesis 1. Then Genesis 11 - 19 played followed by Genesis 2 and then Genesis 20 followed by Genesis 21 - 29. Other books followed the same pattern.
** My alpha-numeric coding begins with "aa1" through "aa9." Then it goes to "ab1 through "ab9," and so on.
*** For a very reasonable fee, you can order the files on disc. I do not know if they are already coded alpha-numerically or not. I was penny wise but pound foolish in that I downloaded each file at no charge. The disadvantage is that I spent time checking to be certain I had not omitted some files. (I had.) And, I had to do my own coding to keep the files in their proper order. In retrospect, it would have been better to pay the relatively small fee and order the files on disc.