Since there has been a lot of recent press and blog coverage of Apple's iBooks Author program, I wanted to point out that an open standards-based alternative exists in the form of EPUB and that we at Altova are fully committed to supporting such open standards.
EPUB is published by the <idpf>, the International Digital Publishing Forum, and is widely supported by various manufacturers and on many devices. The standard is based on XHTML, CSS, SVG, and other well-known web standards and a huge volume of freely available EPUB books already exist today.
From "The Canterville Ghost" by Oscar Wilde, 1906
Let me point out a few useful resources for getting started with the EPUB standard and also outline the new EPUB capabilities in XMLSpy.