Perhaps Naruto would find a book that has stories of his parents. He's always been curious about them. Reading about their adventures, their ideals, and how they were as ninjas would give him a deeper connection to his family heritage. He could also learn from their experiences and become an even better ninja, using the lessons from the book as inspiration.
Well, he might discover a hidden jutsu scroll in the library. It could be a long - lost technique that gives him an edge in battles.
Naruto could find a book that tells the story of a great hero who was just like him, full of energy and a desire to protect. This could inspire him to new heights. He might also accidentally trigger a trap or a hidden mechanism in the library while exploring, leading to an adventure filled with challenges and puzzles to solve.
Well, Naruto might discover some long - lost jutsu in that ancient library. Maybe there are scrolls that hold the secrets to new and powerful ninja techniques that no one has used in ages.
Perhaps in this fanfiction, the secret library is guarded by some sort of magical or powerful entity. Naruto, being Naruto, would try to befriend it first. Once inside, he could find prophecies about the future of the ninja world written in the books. This knowledge might put him on a new path of preventing future disasters and bringing about a new era of peace in the ninja world.
Well, he could gain new powers. Maybe the sentient library has books that teach him long - lost jutsu or give him knowledge about the nature of chakra that no one else in the ninja world knows. For example, he might learn how to combine different elemental chakra in a completely new way.
In a 'Naruto finds a gun' fanfic, one possibility is that Naruto, being curious, might initially mistake it for some strange new weapon from another land. He could try to figure out how it works in his own Naruto - like way, perhaps by trying to infuse chakra into it, which might lead to unexpected and comical results, like the gun shooting out chakra - blasts instead of bullets.
The story in the 'naruto finds a tank fanfic' could also take a more comical turn. Naruto could accidentally set off some alarm on the tank and then start panicking, thinking it's about to attack him. Or he might mistake the tank for a really big and strange animal and start trying to communicate with it in his own Naruto - like way, which would be really funny to read.
In the 'Naruto finds an egg fanfic', Naruto may take the egg to his teacher, like Iruka. They might study it together. It could be an egg of a rare creature. Naruto's sense of adventure would lead him to discover more about the egg, and perhaps it will hatch into a cool animal that becomes his new friend or ally.
He could find the sword in an ancient tomb. This tomb might be filled with traps and puzzles that Naruto has to overcome. Once he gets the sword, he discovers that it glows when near an enemy's weak point. So, he starts using this ability to his advantage in battles.
Perhaps Naruto would use the infinite library to understand his enemies better. He could study the weaknesses of his foes by finding information about their clans or fighting styles. Also, he might find books that could help him train his friends more effectively. The library could be a source of great power for Naruto, not just in terms of combat skills but also in terms of wisdom and leadership.
Well, he might be initially confused. Naruto comes from a world with ninjas, not a modern army base. He could think it's some new kind of enemy stronghold. Maybe he'd try to infiltrate it in his typical ninja way, using stealth and jutsus.