I was searching for "Thanks for the feedback" - could be they just don't have it. I don't have an example on hand but Ive had it happen that my search result was just irrelevant stuff and later I found the book through related categories. Searching for the literal titles doesn't filter properly for me at least.
What book are you trying to search for? I've noticed that they definitely have a lot, but sometimes not everything, especially if the books are newer. I haven't really had an issue with the search function though, what exactly is happening when you try searching for a book?
save