I have found an image that shows the page quite clearly:
The text appears to say, I have taken this off of the wikia but it does appear to be accurate:
The Valyrians were familiar with dragonglass long before they came to Westeros. They called it "zīrtys perzys" which translated to “frozen fire” in Valyrian and eastern tales tell of how their dragons would thaw the stone with dragonflame until it became molten and malleable. The Valyrians then used it to build their strange monuments and building without seams and joints of our modern castles.
When Aegon the conqueror forged his Seven Kingdoms, he and his descendants would often decorate their blades with dragonglass feeling a kinship with the stone. The royal fashion for dragonglass ornamentation soon spread throughout the Seven Kingdoms to those wealthy enough to afford it. Hilts and pommels were and are the most common decoration for dragonglass if too brittle to make a useful crossguard. Indeed, its very brittleness is what relegate it to the great houses and the most successful merchants.
So the only significance appears to be that it was once a Targaryen blade as it seems to be decorated in the same fashion as described in the book.
However, there may be more to it than that as apparently John Bradley, Sam, was told to linger on that page:
“I was told very little about that. When we were shooting that scene, I was literally told make sure that you linger on this page. They were shooting over my shoulder and said make sure to linger on this page. Make sure we get a good shot of this page before you turn the page over,” Bradley said.
“It’s all part of the same universe,” Bradley told HuffPost about that moment, “and all of these storylines, no matter how spread out they feel sometimes, they are a lot of the same storyline and in the equation ... and if you think you saw something you probably did see something. It may not be what you thought you saw, but it just kind of feeds into this idea that [showrunners David Benioff and D.B. Weiss] have a plan, and they are playing the long game, and they are gonna plant the seeds.”
Though that could be referring to the story in general and not just about this dagger.