A friend recently complained that when he did a search on Amazon for Discord's Child, my novel wasn't listed.  I couldn't understand this as a Google search for the title finds it straight away on both the Amazon.com and .co.uk sites.  I tried the Amazon site myself and discovered that if I used the title alone, or my author name (K. S. Dearsley) Discord's Child was top of the list.  However, if I prefixed the title with 'book' or 'novel', as my friend had done, it didn't appear at all.  Instead the search chose books that only had 'child' or 'children' in the title or author's surname.  
Using 'ebook' or the genre 'Fantasy' or 'Fantasy Epic' as prefixes succeeded in finding it.  If the specific title hadn't been used, I could understand it appearing lower down in the search, but not it being totally absent, even if the Amazon search engine regards ebooks and books or enovels and novels as totally different things.
I contacted Amazon and was told that the system was working as it should.  Apparently, even if the words entered in the search are the exact match for a title, the search will show books that are higher ranked, although only tenuously connected, first.  This doesn't explain why Discord's Child doesn't appear on some searches at all.  It seems that if a work is already selling well, Amazon will tilt the scales to ensure it does even better.
So, if anyone would like to look up Discord's Child you'll find more about it on my website, on Goodreads, or by going to http://www.amazon.com/dp/B006KRYYOK or http://www.amazon.co.uk/dp/B006KRYYOK or by searching for the title alone.