Excuse me, but I am thinking in a lateral way. Normally most people have never used search within a book, so it may take longer at first compared to x-ray. But using search on the web is considered a skill, so perhaps by using search inside a book more can develop as a skill?
Though x-ray will be faster, it involves no skill....I mean search is a skill, which may lead to obscure connections to possibilities within and outside the book.
X-RAY ON YOUTUBE:
Kindle Fire HD 8.9 hands-on with X-Ray for video and ebooks