I don't know if it is a horror story, but I bought a kindle edition of a reference work to use on my iPad (it was a kindle-fire book, apparently optimised for tablets) and the app is so slow that searching or flipping pages is useless.

There are cracked PDF's version of the book, which I can search in seconds and flip pages fast, copy content into a google search and use my build-in dictionary to look up words.

The PDF version is everything the kindle version is not: Free and useful.