Wow, that's fantastic. I recently published my own book last month and had a similar experience. Not quite the same profits (heh), but overall it was a great little adventure. I don't really do any marketing or promoting, I'm currently just getting by with a simple link on my website. I tried to bill it as a bathroom reader for the scientifically curious.

http://www.amazon.com/Zidbits-Learn-something-today-Volume/d...

One thing I found is that if you're going to write a book yourself, get someone (preferably multiple people) to check it for errors. Better yet, pay a professional. You may think you can find all the mistakes or grammar errors, but I guarantee that you won't. I learned the hard way.

I don't know if others had a similar experience, but writing an ebook version for the Kindle (through Amazon's KDP) was more difficult than writing an actual paperback. Createspace's paperback publishing seems to be more forgiving.

The nice thing about Amazon's publishing services is that they allow you to update and/or change your books if necessary.