I'm pleased to say (as a collector), that the book is now available in the traditional print format (not that I minded the electronic version). While it loses the interactivity of the iPad version (you have to avoid glancing at solutions), it does allow you to flick through the book in a more familiar manner. Otherwise the differences between the two versions are so minimal, that it simply comes down to a matter of taste.
If you wish to purchase a copy of the book, the current price is
(Note: My review copy was supplied to me by the author)