Unlike the one in S1, this one appears unfinished and can't actually be accessed in the game, but it still exists in the files of the Japanese versions. It has been removed from the English localization, which suggests it's not meant to be accessed.
But what it is, is rather interesting. It's Marlowe's biography of Riou and it changes depending on your actions, but the actions it tracks are kind of weird. Not sure if the game even flags these events in the final game but here's the translated text from the Japanese version.
It also doesn't seem to account for the possibility that Nanami was left in Kyaro at the start of the game, but possibly those pages would just be skipped if that happened.
This would be the longest book in the game by far, but some pages would essentially be two words.
Obviously, any instance of "Riou" would be replaced by whatever name you gave him but it reads easier without a [HERO NAME HERE].
Title: Riou's Biography
Riou was in the Highland camp with his best friend Jowy.
They would finally be going back to their hometown the next day.
But their hopes were destroyed by a surprise attack.
But then they learned that Luca Blight was behind it.
To get away, Jowy suggested they jump into the river.
Riou quickly made up his mind and decided to jump in.
Alternative:
Riou wasn't sure at first, but Jowy pleaded with him to jump in the river.
When Riou woke up, he was a prisoner of a mercenary army.
One day, risking his own life, Jowy came to rescue him.
The two of them ran from the fort, towards their hometown.
Alternative:
Riou wasn't sure about leaving the fort, but he decided to go to his hometown in the end.
They reunited with Nanami in the town of Kyaro, but all three of them were captured.
However, with the aid of Viktor and Flik, they managed to escape.
Just as they were about to leave their home, Nanami asked:
"Do you think we can come back?"
Riou reassured her that they'd come back some day.
Alternative:
Riou looked at Nanami and said coldly:
"I don't want to come back."
After living in the fort for a while, he met Pilika, a young girl who had saved Jowy's life.
She had a request to make of Riou which he
accepted gladly.
Alternative:
reluctantly accepted.
When they returned they saw the atrocities done by the Highland Army.
They joined the mercenaries, but were defeated.
With the fort in flames around him he
tried to get away as quickly as possible.
Alternative:
risked his life to try and save Pilika.
After escaping the fort, Riou arrived in Muse, but the Highland Army wasn't far behind.
As Muse fell, Jowy and Riou went their seperate ways.
After escaping, the group arrived in South Window where they
reunited with Viktor.
Alternative:
reunited with Bear.
Apple recommended that they recruit Shu, a military strategist, to help them fight off the Highland Army.
However, Shu would only join if she could find a coin he tossed into the river.
Riou and Apple braved the freezing waters together, to find the coin.
Alternative:
At Nanami's behest, Riou reluctantly joined the search for the coin.
When Shu saw this, he decided to lend them his power and successfully beat the Highland Army.
After this battle, Riou
had no choice but to become the leader of the Orange Army.
Alternative:
took on the role as leader of the Orange Army.
After defending Two River he headed to Greenhill.
There he found a girl named Nina
and saved her,
Alternative:
and ignored her,
and saw an innkeeper being accused of harboring a spy that he
tried to help.
Alternative:
pretended not to see.
Eventually, he was able to learn Teresa's location
and mistook Shin, Teresa's bodyguard, for a ghost.
Alternative:
along with Shin, Teresa's bodyguard.
Though he managed to find Teresa, she decided to give herself up to save her citizens
and Riou had no choice but to save her.
Alternative:
but Riou saved her from being taken to the Royal Family.
After returning from Greenhill, Riou went to meet with the Knights of Matilda.
There, he tried to save the refugees, but was unable to,
Alternative:
There, he left the refugees to die,
and he was not able to get the Knight's cooperation, though he brought in Camus and Miklotov to help fight against Kiba.
The battle ended in victory for the Orange Army and after they captured them he
tried to cut off General Kiba's head, but was stopped.
Alternative:
offered General Kiba to join him.
Then, in the battle against Luca Blight
General Ridley was captured, but they won.
Alternative:
they won.
To his delight, the new king was Jowy.
Riou went to Muse to sign a peace treaty with Jowy, but when they arrived Jowy asked him to surrender instead.
Riou was about to surrender
Alternative:
Riou refused
when suddenly Viktor appeared and with Shu's plan managed to escape from Muse.
Then Riou went to Tinto to try and bolster his army
and realized that he had to keep fighting, despite his doubts,
Alternative:
but tried to run away with Nanami, but returned to the fight after realizing that he couldn't run away,
and helped Viktor and the others defeat Neclord.
After returning to North Window Castle from Tinto, Riou found his life in danger.
However, Riou was able to turn the tables on Lucia the female warrior, his would-be assassin,
Alternative:
His friends came to his aid before Lucia could kill him,
and they went on to liberate Greenhill.
There he was once again confronted by Jowy, who asked him again to give up the fight.
But Riou responded that their battle could not be avoided.
Alternative:
But Riou said he couldn't just give up.
The war was finally heading towards the final battle.
Conditional:
With the power of the 108 Stars, Riou broke the seal on the Bright Shield Rune, and
Riou took the hopes of everyone onto himself.
He set out for Matilda, but it was there that he would lose Nanami, his one and only family.
With a heavy heart Riou decided to invade Highland
to put an end to the war with his own strength, and
Alternative:
even though he hated having to fight, he had no choice but to
confront Luca Blight's final weapon, the incarnation of the Beast Rune.
But for Riou no enemy was too difficult to beat and he took down the Silver Wolf,
Alternative:
But even though the battle was hard, Riou managed to defeat the Silver Wolf,
but when he entered the throne room there was no sign of Jowy.
With the war already over, Riou quietly left the throne room and
Alternative:
Riou tried looking for Jowy, but was unable to reunite with him, he left the throne room and
he returned to the people waiting for him, celebrating his victory over the Kingdom of Highland...
To all the people who loved him...