Does anybody have any experience with selling books like this outside of the software realm? By which I mean publishing beta books as you go or bundling other resources. and charging a premium. It seems to be something that the software community finds acceptable, but does this extend to other fields? Non-fiction or fiction.
You asked about selling books outside of the software realm. The In 30 Minutes guides are aimed at mainstream users, and I found through some early pricing experiments that attempting to charge more than $10 for these types of ebooks is very difficult. I have also found through more recent experiments that pricing ebook versions less than $5 leads to an immediate and sustained rise in sales.
I sell ebooks through Amazon, iTunes, and B&N as well as PDF versions on Gumroad. I have also made mobi/epub versions available on Gumroad, but very few people buy them -- Amazon, Apple and Android tablet manufacturers do not make it easy to transfer these types of files to their devices, which is a roadblock to most people in my target audience.
In my limited experience promoting fiction, factors such as categorization, whether or not the book is in a series, and the number of reviews on Amazon or Goodreads influence awareness and purchasing decisions. Because there is so much competition in the fiction realm, and most new titles by relatively unknown authors are priced at $4 or less, I think the reaction to an expensive fiction ebook by another unknown author would be negative.
For anyone who is interested in self-publishing, I wrote another HN post last year that a lot of people found useful. It includes tips on how to get started using a lean approach to writing, production, and marketing (2). Good luck!