Can I ask you one thing? There's really a 5th author in the library room? Which is the Sangerman's library? °_°
I ask you because when I played it (I have the game in Italian, because I'm from Italy XD) I found only 4 libraries (before entering in the room with the projector to use the film) with 4 authors: Flamel, Fulkanelli, Agrippa and Paracelsus (in the italian translation is "Paracelsus" if remember well...and I don't know why in the english version is mispelled in "Paraculeus"...°_°)
Anyway I found only this four authors...but I never seen Fiona commenting about a fifth author called "Sangerman" O_O
Sorry for the trouble, it's only a doubt that I have...but I think that maybe in the Italian version this author was not included....
There is apparently a bookshelf where Fiona says "Sangerman is the author of these books". Just search them carefully, you'll find it. In the underwater library where you need to replace Flamel's book, Agrippa's book, and Furkanelli's book to their respective place.
Finally I found it! You're right, there's also Sangerman! I have made some research and this author (like Agrippa, Flamel, Furkanelli and Paraculeus) is a tribute to alchemy...and in particular to Count of Saint-Germain, who maybe was the last alchemist...I think that ultimately all these alchemists have been a source of inspiration to create Lorenzo's character...