The summary misses a key point. Yes they scan and store the entire book, but they are _NOT_ making the entire book available to everyone. For the most part they are just making it searchable.
Agreed that it's not in the summary, but as you correctly note, it's just a "summary". Anyone who reads the underlying blog post will read this among the facts on which the court based its opinion: "The public was allowed to search by keyword. The search results showed only the page numbers for the search term and the number of times it appeared; none of the text was visible."
So those readers who RTFA will be in the know.
The counterargument against excluding evidence is: you committed a crime; this evidence shows it. Why should you get off just because the police did something wrong? That didn't magically make it so you didn't commit the crime, it just turns the whole process into a game with arbitrary rules.
In any event, my hypothetical was more akin to Illinois v. Rodriguez, where the Court held that as long as the police had a reasonable belief that the person giving consent to search was in fact authorized to do so, evidence won't be excluded, even if that person did not have actual authority.
That being said, I will qualify that I believe in some states actual authority is required, but at the Supreme Court/Federal level only apparent authority is needed.
Kind of over the top but in a close case it might convince a judge that whatever pretext the police came up with to enter was unreasonable. Also might be a good idea to have a motion-activated camera with sound to capture anyone who would be in a position to read it so you could capture whoever enters, if you really want to be careful.
For example, the cops generally need a warrant to enter your house to search for drugs unless an owner grants permission to the search. If you're staying over at my house while I'm away, the cops ask you for permission to search the place thinking it is your house, and you say yes, anything they find is admissible because they had a good faith belief they were conducting a legal search.