Why has the search feature in Books changed?

Before the current update I used to be able to search specific words in whatever text I had uploaded to iBooks, whether it was a pdf or epub and the search results would remain on the previous screen. Now when I search something once I select a page and attempt to go back all the search results disappear and I have to start the search all over again. This is highly annoying and inconvenient. This update has eliminated one of the best features in Books and it is very frustrating