Literary candle.

Does she have an all-time favorite book or series? Get her a matching candle to serve as a constant reminder of it. If she has multiple favorites, then get her a book-scented candle so she can always be reminded of the joy to be had when cracking open a new book.

Bookish mugs.

Get her favorite book quote on a large cozy mug. She will love sipping coffee as it rains, with a good book in her hand.

Take her to the bookstore.

Go on a date to the bookstore! Take her to a cute second-hand shop and each choose a book for the other. Then, after your done, sit down with coffee and food, and read!

Book date.

Prior to seeing her, get one of her favorite books and read it. As you do so, highlight and circle and underline favorite parts, quotes, and things that remind you of her in it. When you give it to her, she will not only be touched by the fact that you read one of her favorite books, but that she will get to re-read it and see it through your eyes.

Take her on a date from a book.

Find a cute date idea from one of her favorite books! Whether it's stargazing in a field, or doing an extravagant series of things, she will love the fact that you took the time to research and reenact scenes from her books.

Go bookshop hopping.

Figure out where all the bookstores in your town are and visit each one. Make a game out of it and try to find the prettiest cover, ugliest cover, funniest title, etc. End the night with dessert and coffee.

Blackout poetry.

Take her to Goodwill or a second-hand bookshop and each pick out a book. Then, go to a fun coffee shop, back home to a cute dinner, or a picnic. With two pencils and sharpies, use the words on the pages to make a funny story or beautiful poetry. Blackout all the words you didn't circle with the pencil, leaving a creative poem. Have fun with it and write each other love letters, inside jokes, etc.

Book chair. 

Reading isn't the most comfortable thing to do. Get your girl a nice little chair where she can keep her coffee beside her, her favorite books in the holders, and read comfortably.

Bookopoly

Have a fun game night at home and battle it out over this fun twist to a classic game! Keep it interesting and have books you can "buy" with the remaining money at the end.