Getting it right in (digital) print
When you consider the countless different mediums the 'printed' word is used for, its no surprise how ebook formats are in a constant state of change. As of writing this, there are around 25 formats in use today; the most popular being the open source EPUB format which is pretty much supported across the board (except on Kindle devices frustratingly, although there are certain kits which let you convert your EPUBs in to a suitable format for Kindles however).
Luckily there isn't much of a learning curve getting your content ready for ebook distribution as most formats (at least all of the ones I experimented with) are essentially packages of XML and CSS files. EPUB has great support for CSS3 too but devices are understandably slow to catch up.
I could waffle on for hours but there are plenty of seriously smarter people than me who have published much better resources on the subject of ebooks and their format types. At the top of the pile would have to be Liz Castro's in-depth insights in to EPUB files which essentially became the backbone of everything I've learn't on the subject. I highly recommend buying her guide: EPUB Straight to the Point: Creating ebooks for the Apple iPad and other ereaders which she continually updates with other mini-guides as well. They're all really well written and a must read for anyone who wants to start figuring out ebooks. Smashing Magazine also have a wealth of information on the subject.
How to solve a problem like Open Minds
The EPUB format seemed like the clear choice in translating 'Open Minds' in to a digital format. I began prototyping a few sample spreads using Liz Castro's "Fixed Layouts" guide as basis. The results looked pretty promising but because I had to hard code the entire thing, the process was pretty long winded and not ideal. The magazine typically had 15 - 20 uniquely designed spreads which, in my opinion, really needed to be retained in the digital copy as a form of visual consistency.
The approved solution was actually sitting in front of me the entire time. iBooks Author is a free WYSIWYG ebook editor from Apple which can produce rich layouts quickly and effortlessly and also includes a bunch of built in 'widgets' so you can add things like interactive images, videos, audio, and polls by just dragging and dropping to your layout. If you're used to designing in programs like InDesign, then this will be pretty easy to pick up. You essentially build layouts for both portrait and landscape (although you can disable portrait mode). It may seem like double the work, but there are a few restrictions in place especially on portrait, where you're stuck using a predetermined layout for both body copy and any widgets you've used.
This can work out to be a double edged sword - on the one hand, you can guarantee a conformed layout in portrait, so you can focus all your time on making landscape looking great; on the other hand, if you decide to make a black background with white body copy on landscape for example, it can be really tricky to get the black background to display in portrait. I ran in to this problem a few times when translating 'Open Minds' and ended up having to compromise on a few colour choices I would have liked to do. Luckily in portrait you get free reign of the header area so you can make visually interesting introductions to your articles.
iBooks actually do use the EPUB format, but with a few differences in its CSS tags, its unfortunately incompatible with the EPUB standard. This essentially means iBooks Author files can only be viewed on iOS devices with the iBooks app installed. This can be a big issue if you want to have your eBook available on as many different devices as possible. As of writing, iBooks Author is the only application of its kind for making visually rich and interactive eBooks relatively painlessly, so unless Apple decide to make iBooks available on other platforms you're unfortunately stuck on iOS for now.
The results iBooks Author can produce speaks volumes for ebooks and the future of digital publishing as a whole, however its restrictions to iOS devices is a big shame. As the open source EPUB format seems to be the leading standard for ebooks at the moment, I'd very much like to see an app in a similar vein to iBooks Author, which uses the EPUB format properly so your product can be viewed on as many devices as possible.