Audiobooks are amazing because they present your work to a new slice of market. People who enjoy audiobook might not read at all, because of time constraints or personal preference. For example many commuters devour audiobooks.
So, how do you produce an audiobook?
Easy way: go on http://www.acx.com/ and hire a narrator to read your book. You will have to split royalties with them.
-A decent quality microphone: I borrowed a good XLR microphone from a friend and connected it to my computer. XLR refers to the three pronged jack that allows you to plug in the mic. XLR mics are better. To avoid buying an expensive mixer I bought a “Blue Icicle” for about $50, which takes the XLR and has a USB out. You could also use a USB microphone. The quality is supposedly lower, but with the parameters I will give you you can see if it’s going to do the trick

-A quiet space with preferably no windows, no AC, no fridges or humming appliances or lights. I found closets to be ideal (in all other matters of life I do recommend coming out of closets.)
If they are packed with clothes or boxes it’s even better because these “soft” objects absorb sounds. Avoid hard surfaces that might create echoes. If have an echo problem, cover your working surface with a blanket.

Detailed instructions will change based on the software you use, but RMS buddy will show as an “effect” you can select for your track.
For Garage band: Create a new project (either “voice” or “podcast”).

1-Determine your background noise. Hit record and do nothing, say nothing, don’t move. After a minute or so, stop. Deselect all effects except RMS buddy. Double click on the RMS buddy icon and re-listen to your recording: you want your average RMS to be less than -60 (for example in the figure above it’s -86).
2-Before you start: work on your enunciation and pace. You will have to be clear and consistent. Personally I hate narrators that read like robots and I do a little interpretation. Check the pronunciation of words you are unsure of. I read from my monitor to avoid the sound of pages turning. You will have to make no noise. No clicking of the mouse, no coughing, no phone buzzing, no computer fan starting (SSD computers are ideal for recording because they are silent).
4-When ready to start, hit record, set up your page then wait a good five seconds before you read. You will edit this part out, cutting all clicking and fumbling noises. When you finish a chapter wait at least ten seconds then click off. You will need to leave five seconds of silence (no clicks!) at the tail of each chapter.
5-Before you record a whole book, make sure the quality of your chapter is what you need. When you read, you need your average RMS to be between -23/-18. dB You can fiddle with the effects to make your chapter sound ideal.
Below are my settings:
-Compressor (double click on it to expand it): this is what will allow you to change your average RMS if needed. If you need a higher RMS, increase your gain (beware of distortions!) My settings: threshold -28, ratio is high, attack 17 ms, gain 16 dB (or as needed)
-AU low pass: between 12 and 24 KHz (0 dB)
-Pick limiter: this will also affect your average RMS. I set my pre-gain at -3 dB.
6-While most people to all the editing at the end, I like to do one chapter at the time. Listen to your chapter again, while following on the text (this is amazing for proofing, by the way!). Check for mispronunciation, mishaps, and noises. Go back and record again parts that need editing. When the chapter is ready cut out the lead and trail silence leaving one second in front and five in the back.
7-Export your chapter as an MP3 at 192 kbps, stereo, var speed. I title my Mp3 Ch x, title
8-Once you recorded all of your chapters you will need: Opening credits (Title, author, narrator, copyright owner and year of the book and the audio version)
Closing credits (same, plus anything you want to say about upcoming titles, your blog etc…, keep it brief!), a five minutes sample (Some authors record something special, some others just select five minutes out of a chapter).
9-If you want to use music you can find royalty free music at http://incompetech.com/ just make sure to acknowledge the composer in your closing credits. If you want to use sounds in your audiobook, you can find royalty free sounds at https://freesound.org/.
10- Calculate an average of 100 hours of work for an 8 hour audiobook.
I wish I had this guide when I started! Remember to pay it forward and help other authors get their books out there: nobody can write your story ^_^
Below is an example for you. Notice the lack of background and mouth noises. Notice the pace, pauses, inflection, and enunciation. Yes, I do have an Italian accent, but it only adds to the charm since the book takes place in Italy ;)

Check out my audiobooks here, they are all on Audible! (*beams with pride*)

Who am I to give you advice?
I am the very proactive, part imaginary author of the Italian Saga (#TIS)

FYI: The books are recommended for anyone 13 and above, but most of my readers are adults.