The article Should You Turn Your Book Into an Audiobook on Audible? by Matt Stone gives some insights into things that may be difficult when you want to turn your self-published book into a self-published audiobook. Here is some information that may be interesting for the scope of this question:
If it’s got a lot of pictures in it and relies on those images for step-by-step instructional purposes, an audiobook version is going to be pretty lame. Sure there are some cookbooks on Audible, but seriously. A cookbook audiobook?
If your book relies on too much visual information it might not be a good idea to turn it into an audio-only experience. This may seem quite obvious for people who mainly focus on novels, but theoretically it might be relevant for them, too. Imagine if you were writing a fantasy novel and you had a map at the beginning, which you feel is important to understand the novel. (Personally I would say that's a pretty bad practice, but it might give you some ideas about what to look out for in your own work.)
Another interesting article from the same site is How to Write an Audiobook Script Like a Pro.
Ask yourself these three simple questions to see if you’re ready to get your book published as an audiobook:
- Has your book been professionally edited and proofread?
- Have you edited your book yourself at least twice before starting to write the audiobook script?
- Have you done everything you possibly can to make your book the best book it can be?
In the article is again a mentioning of images:
If your book says,
“Refer to the image on the next page.”
You’ll definitely want to change that for the audiobook script to something like:
“Refer to the image in the Audiobook Companion document that comes free with your purchase of this audiobook.”
It also mentions difficult words (emphasis mine):
While you are making your edits to the audiobook script, make sure to take note of any words that may be rare or hard to pronounce, especially technical jargon, foreign words, acronyms, and your name. Create a list of these difficult-to-pronounce words and send them to your narrator ahead of time so they are prepared. This will reduce the time it takes to edit the audiobook after it’s been narrated.
If you have a large list of words, simply record a video or audio file (mp3) of you pronouncing those words correctly and send that recording to your narrator.
The article How to Make an Audiobook and Self Publish on Audible Today from Bryan Collins mentions that it's easier to narrate a non-fiction book than a fiction book. The reason for this is that there is less need for switching the voice when reading the book. This means that a non-fiction book will likely cost less in production than a fiction book, as you will end up with more time for the narrating and mastering process.