A fair bit of work went into converting the series into ePub and iBook formats. The maps are not included as it really is more trouble than it is worth trying to create a good quality map that can be read on a small screen. The other difference is that The Longest Night and Crossing the Rubicon are one volume, as was originally intended. At the time of producing them for Kindle and a matching paperback on Amazon the sixteen maps had pushed the paperback file size to over the maximum permitted by the printer, which caused a very reluctant split into two shorter books in order to mirror the Kindle. Without maps in iBook and ePub formats there are no such issues and the series is four volumes instead of kindles five.
The books all come in hard-cover copies as well the paperback and electronic versions. Unfortunately audio books are frighteningly expensive to produce so they will not be happening any time soon.