You search through the rightmost bookshelf first. You look through all the books, all seem boring and uninteresting. Most of them are books about philosophy and psychology. You notice that none of them have authors, they only have unnecessarily long titles.

While scanning this old cobwebbed bookcase you spot a worn out paper between two book.

You found 1 (ONE) TATTERED NOTE! It appears to have a 0 (ZERO) written in it. There also seems to have been some liquid drawn on it but you can't make out what was written with it.

You search through the other bookshelf which has similarly boring books except these seem to be about english and history. These books also have no authors. You find 1 (ONE) BOX OF OLD MATCHES on top of one of the books. They seem like they still work.

You might be able to check if the TATTERED NOTE has invisible ink on it with these matches but you'd need to put some form of fruit juice on it so the paper doesn't burn.