...why?
This game is... very linear. As in, "visual novel with minigames" linear.
Save for Book 4's Love Route, the only points you can get stuck are by: not ginding/doing the current minigame enough to get the item you need, or didn't check around enough to see all scenes available. The closest to blocks I remember is book 2, love route you have three endings that are exclusive (meaning if you go to one you can't see the others), and you can just save before making the choice and see all three, and slave route you have decisions that can change some part of the ending like freeing the slaves or having good karma.
And you can start from any book, you have an order but nothing forces you to follow them.
Unless you want the saves to be the near end of every book, where you can still see most of the repeatable scenes? But it is not 100%.
(well, I think you may also mean the book 4 slave route cards minigame, where you can keep playing for a random concept art?)