Theory of abstract proportions
'Elements' was written by Euclid.
The fifth book is called "A Dangerous Path".
Euclid of Alexandria or Eukleides
The name of the fifth book was Waterwings but they changed the name to MAX
everlasting is the name of the last book
the name of the 5th 39 clues book is the black circle
Elements
The Last Olympian
the last olympian.
Book 5: Percy Jackson and the Olympians: The Last Olympian
Euclid's Elements is the name you're after.
hemroids