I'm currently in the process of transforming our former junk room into a functional space. We had always planned for it to become a dining room, but now it feels like that would be a space that just sits unused (aside form special occasions) and accumulates clutter.
A room that would serve a lot more purpose during this stage of life would be a study/library. Nathan already uses this room as his home office and it'd be great to use the rest of the space to read and relax, play games with the kids, and display some of my favorite finds.

Here's a few tips for creating a home library even if you don't have a large space to work with.
Lots of books, obviously

If there's one thing a library needs regardless of size, it's books. You can fill your library with favorites you already have or hit up thrift shops to build a collection of worn and weathered spines.
The best place to find the best books...

If you want beautifully old books at an amazing price, garage sales are your best bet. Also watch for library or school sales where they're clearing out old inventory.
Take it to a new level

A favorite feature in my own library is a pair of vintage ladders I found on Facebook Marketplace. I think adding a ladder makes a home library feel so much more official even if it isn't a legit, rolling library ladder. Watch marketplace for a great deal or if you're in the right area, you can find a lot of beautiful ladders at barn sales.
Personalize your space

Add some unique, "academic" details to complete the look. Globes, busts, a magnifying glass, etc. I have a full list of ideas for what to include on shelves in The Worcester Run Guide to Shelf Styling if you need inspiration.
Come and sit a spell

A library wouldn't be complete without a place to sit and read. Find a pretty armchair and maybe add a small side table too so you'll have a place to set a cozy drink.
The finishing touch

To me, a library should be a cozy, quiet retreat you can hide away in. To create the optimal cozy space, include a candle that smells like books, a fireplace, or something you find relaxing.
No home should be without some sort of library and hopefully this list has given you inspiration for creating your own cozy, book-filled retreat.