I DM for a D&D (5e) group in a custom campaign setting which I worldbuild as we go. One of my players is very much interested in the history and lore of the world and often tries to find out bits of knowledge by going looking for books and the like. I'm really happy that he's so interested in my world and it often gives me good opportunities to think some more about certain aspects of my world, but I'm not sure what the right way to hand out this information would be.

What I often do is improvise the name of a book he finds during the session, then write about a page or so of summary about the the subject from the fictional author's viewpoint. The problem I see with this approach is that it feels sort of unnatural to have a whole book consist of a single page of information, which also happens to neatly summarize its content matter.

But I do want to do written lore. If, for example, I were instead to tell the player something like "After reading the book you find out X, Y and Z.", it feels like straight-on, dry exposition, the player gets nothing tangible (no frayed scroll/page) and I don't get the fun of writing from an NPC's point of view.

How can I deliver written lore from my in-game universe to my players, without making it a dry exposition? Is my current approach a valid one for this problem?

Add brief lore based descriptions to many objects, not just books.

Lots of hand crafted objects should have references to the lore of the world. Subtle examples include: Symbols of deities, makers marks of a famous smiths, allusions to heroes or kinds of the realm, etc.

Keep it simple

Providing brief summaries makes information tractable and trackable. Multipage volumes make distilling information difficult.

Let the players figure it out.

Simply state a succinct summary of the relevant lore, legend, or description. Add as much or little detail as desired, but don't call out specifically, "you learn X." The players reading it will either learn and recall the information or not.

Example Summaries

An entire book about the adventures of Robin Hood could be summarized as, "a story of the famous rogue that robbed from the rich and gave to the poor. The exploits detail heroic skill with a bow and arrow." For a first introduction, that's sufficient and succinct.

Subsequently, a bowyer hawking their wares could then make a passing reference, "this is the same kind of bow Robin O'Hood used to draw!"

Finding slightly conflicting subsequent lore can add interest. For example, a depiction of the hero on a tapestry, "the image of Robin Hood single handedly fighting 5 men at arms with a longsword and dagger. Conspicuously, he doesn't have bow on him, and the inscription is 'Robin Hood Master of the Blade.'"

Make loot interesting

Finding artwork and valuable tools or weapons can be made distinct be referencing lore. E.g. "The weapons rack has a few spears and a half dozen short swords. The fighter recognizes their quality, and the rogue notes that one of the swords has the mark of [some previously encountered blacksmith] engraved in the pommel." These can provide lore and story hooks.

Lore can't be forced.

In most stories and games, a lot of lore goes untold and unheard. Tolkien had entire continents that shaped the world of Lord of the Rings, but while the effects of the history were seen, the actual stories were not (Aragorn's ancestors were originally lured to middle earth by Morgoth, first lord of Mordor, who created the balrogs!). Skyrim had entire libraries of books and dialogues about the dwemer, but most people who played the game were unaware of it. Dark Souls and Bloodborne have one of the most in-depth lore, but it's so broken up and hidden across the various item texts and dialogues that whole communities need to work on decoding everything, and most don't bother.

Having people care enough to read lore is one of the biggest challenges a world-builder can come up against.

So how do I make people care?

Now, you can go into the psychology of gaming and motivations, but the simple answer is "Tie your lore to what your players care about."

With DnD, the best ways to accomplish this comes from the three things that drive DMs crazy. Item hoarding, murderhoboing, and players hogging the spotlight. Old players or new, players have fun with cool items, cool battles, and getting the chance to show off their characters.

If you want to have your players care enough to read books, you might think about throwing down some pretty blatant hints. You find a broken sword that seems to radiate holy and unholy energy, and an identify spell reveals that, if fixed, this "ashkeeper's godslayer" sword is super powerful. Now the phrase "Ashkeeper" and "Godslayer" is tied to potentially getting some sweet loot.

Now they might read a page about ashkeepers, but a full book might still be too much. Now they face a horde of undead with some unusual ability, like zombies with truesight and who deal holy and unholy damage, and these are zombies of ashkeepers, and the symbol of the ashkeepers are all over their clothing. Suddenly, learning about ashkeepers not only might grant a cool sword, but also might tie into truesight, and maybe even some cool super zombies.

Finally, look into weaving ashkeepers into a character's backstory. Maybe one of your player's characters has a coat of arms, and the ashkeeper symbol appears in their crest. Now the players can have their character as the star of the week if they can push the ashkeepers as a central role.

And, by doing this, you can build up interest in the lore and also start sharing the lore. Just by what I've written, you know the ashkeepers wield holy and unholy powers, were formal enough to influence family coat of arms, they use enchanted swords, and are turned into zombies with extra powers. From there, you can build out the lore.

The best way to know if a party is ready to get heavier lore is if they begin actively looking for it. If they start looking through libraries for books with ashkeeper symbols, or go to a bookstore in a town looking for ashkeepers, or show off the broken sword and ask about ashkeepers.

What should I avoid?

In a lot of games, there's an obstacle I've heard called "paper fatigue". Players are constantly having to refer to their sheets and scan them for ability scores and modifiers, skills, feats, features, attack bonuses, etc. It's a lot of text, a lot of scanning, and it can be very frustrating and exhausting to go through binders every time you need to find a number. Adding more paper to this situation can be the straw that broke the camel's back, and you might lose party investment and immersion.

Also, avoid railroading. If the party doesn't want to read lore, don't punish them for it. If your players are more interested in running the story than digging into the history, don't punish them for it. You may need to find a different party.

Learning requires context.

If the player knows little, they will absorb little from reading a book. If they know a lot, much of the book will be things known to them, but they are capable of finding something new and interesting from it.

Thus for a bit of book, you should have some lore ready. Maybe at different "depths" with different DCs.

The player makes a roll, and they are told a general overview ("the book is about the history of grain shipments in the middle kingdom") regardless. Then as a result of the check, you say:

Of particular interest is a passage about the Lord of Starlight. He appears to be a Fae noble with some connection to the Far Realm. This passage in particular:

and insert some in-universe prose.

Character knowledge is not the same as Player knowledge. The Player reading the book of lore could get more or less information than the Character should.

By passing out snippets of lore, plus having skill checks on demand, you can provide the Player with the knowledge the Character has as needed. And avoid long dry expositions.

You can see this effect in many works of fiction. A character reads a long book, but they don't transcribe it into the fiction. Instead, useful bits of information are transcribed, often quotes.

Also, you can hand out tokens. Read a book on the trade between Turath and the Fae? Get a token about it; later, you can use it for advantage on a check involving Turath or the Fae. Sort of a limited-use inspiration.

You can limit a character to a number of such tokens equal to their proficiency bonus, representing how many such things you can keep in your head at once, and only on trained skills. Players will then be encouraged to research things they think are useful and match their character's skills, but not everything, to get these tokens.

I see nothing wrong with your approach.

If you were to write a life-like-sized book for every little detail, that would become a huge burden for you and the player both, and it would detract from the experience, rather than enhancing it.

You can also lay that nagging feeling of 'unnaturalness' to rest by noting how it is not uncommon to find a summary chapter even in many real-life books, especially those written in centuries past. In fact even when the original author did not include such a chapter, modern publishing houses put summaries or excerpts on the back of the book or inside its cover for the would-be purchaser's convenience.

From the games industry, I would recommend the Elder Scrolls series as an example of lore done right. The world of Tamriel is littered with writings of various length, always in-character, sometimes contradicting each other, or offering separate theories and world views, even. Longer books are often split into several chapters. You can find an extensive collection here, and more lore (including lists of quirky item descriptions from Elder Scrolls Online) here.