If lost or destroyed, a new copy can be obtained from the bookcase in your Player-Owned House made through Construction.
Below is the text you can read from within the book.
15th of Bennath
We made landfall today. Archer was right - the caves are vast, and there's more than enough room for the Empress.
What's more, the island's inhabitants seem to have no idea the caves even exist. Thank the gods for the incurious minds of everyday people! This place is going to make an excellent hideout.
17th of Bennath
We've started securing the caves. Williams has installed a few booby traps, which should keep out any unwanted visitors. The place is pretty unremarkable, although I did find some large, seaweed-covered pods in one of the caves that are rather unusual.
20th of Bennath
Today Captain Mulligan ordered me to investigate the north-western chamber, where I found a number of holes in the wall - large, evenly spaced holes, as wide as a man.
I peered into one and saw something inside - a large crab, I though - and gave it a prod with my harpoon. It didn't move, so I got Sigfried to help me drag it out. I wish to Saradomin I hadn't.
I don't know how to describe what we found. It was like some unholy fusion of man, crab and squid. Neither of us said a word - we just stared at the creature in silent horror.
Then suddenly it stirred, and before I could gather my wits, Sigfried ran it through with his spear. It made a horrible gargling sound as it died.
I ran to Captain Mulligan and told him what we'd found. He followed me over to the creature and took a good long look, then said 'throw it in the water', and marched off. I ran after him, begging him to let us leave, but he said the caves were too valuable for us to abandon them.
I went back to Sigfried, and together he and I hauled the creature into the sea.
21st of Bennath
I slept badly last night, had nightmares. Word of the creature has reached the others, and most want to leave. Fortunately, this seems to have convinced Captain Mulligan - maybe he's realised that abandoning this place is preferable to alienating his crew - and he's given orders to prepare for departure.
If it were up to me, we'd leave straight away, but Mulligan wants us to gather up everything of value first.
22nd of Bennath
I knew we should have left sooner! Now it's too late.
It happened at about midday. Anders and Percy were carrying some lumber across the middeck when Anders lost his footing and fell. He landed awkwardly and somehow managed to knock one of the cannon[sic] off its carriage, and as the gun hit the deck it went off.
The noise was so loud I thought at first the roof was caving in. Then, as the ringing in my ears started to subside, I heard a sound - a scurrying, scuttling sort of sound - that sent a shiver up my spine.
Suddenly Anders gave a cry and pointed towards the cave wall. I followed his gaze and saw a dark shape emerging from one of the holes. Then I saw another. The scuttling sound grew louder, and at that point Captain Mulligan appeared on the deck. He shouted 'to arms!', and everything descended into chaos.
One of the creatures appeared on deck, followed moments later by two more. Those who had swords drew them. I heard shouts, screams, and the ringing of steel. I saw Archer fall, his face covered in blood. More of the creatures swarmed onto the ship. Then I saw Mulligan, held by one of the creatures, screaming as he was carried off into the darkness. The panic rose in my chest, and I turned and ran.
Now I'm in the southernmost cave, with the creatures on one side and the raging sea on the other. To head out into the ocean would be suicide, so it looks like I'm going to have to face them. I know one thing for sure - I don't want to suffer the same fate as Mulligan.
They're coming. I can hear them.