You can do either technical or fiction books on all services.

Leanpub is 99usd to start, but they have tools to help you write the book and generate web pages, epub, pdf and mobi. You can also in turn take those files and use them to publish on Amazon KDP and Apple iBooks.

As a side note, on LeanPub, there is also book styles for Business, Fiction and Technical books. It's under "Writing -> Book Theme"