I think 616
The book has 361 pages.
Royal Assassin has 580 pages.
By Royal Command has 354 pages.
Royal Exile has 464 pages.
The Royal Pain has 352 pages.
Royal Escape has 512 pages.
Royal Robbins has 96 pages.
Royal Flash has 256 pages.
There are 361 pages in the Battle of the Labyrinth.I only have paper back and it is 361 pages, I do not know the answer to hard cover.
Into Battle has 208 pages.
The Visit of the Royal Physician has 387 pages.
Splendours of Royal Mysore has 760 pages.