Being librarian of a library that was always moving was a tough job. Luckily, Professor River Song was up for it. The books were her friends, and the library her home. She had a set of rooms just outside of the library, but she never used them.
Students liked River, and River liked the students. She had a few favourites, like that little first year girl, Clara, who had such an enthusiasm for Charms, and seemed genuinely enchanted by the library, and its constant rustling of paper wings and the gentle shifting of bookcases. Clara seemed to be in here half of the time she wasn't in lessons.
Or Fitz, and his strange but incredibly sweet friend, who had once spent most of the night huddled over a table perusing book after book of names. The library liked Fitz's friend, and had pulled in close around the pair to make sure they weren't disturbed. River had flown over the top of them, balancing precariously but with great skill on top of two thick tomes on wizarding law. The books didn't like being stepped on that much, but they understood the need for her to check on the pair.
The books kept River company on the days when only a few students wandered in and out of the maze of shelves, or even when not a single person entered (this was mostly during the breaks when there were no students around and many teachers went on family visits). Each book was unique in personality. Her favourite was a slim Potions textbook who would flutter down to her shoulder and nestle against her curly hair, pages whispering inaudible secrets with every movement.
There were books that would chase each other in playful flight around the ceiling, books that would sit patiently on shelves and jump away when a student reached for them. There were books that followed River around in a rustling, bustling group, tripping over themselves and competing to perch themselves on her head. The books had minds of their own, even more so than the shelves, that moved around whenever you turned your back.
Sometimes, students would come in looking sad, or lonely, and River would whisper to her crowd of books and they would flutter off and surround the student in a rustling, concerned crowd until the student cheered up.
As a young Ravenclaw student at Hogwarts, River had spent a great deal of time sitting in the library perusing textbooks and fiction books and history books and whatever books she could get her hands on. She had simply not been as practical as most of the students, she had to force all of it through books.
She had stayed on after her NEWTs as the assistant librarian, and eventually taken over when the older librarian had gotten too old to deal with the books at all hours, developing such a strong affinity with the books that she could even control the shelves to an extent, an ability only a few of the professors and students seemed to share.
It was often rumoured around Hogwarts that the library was somehow infinite. No one had ever reached the end. Bigger on the inside, shifting and changing and maze-like. River thought it probably was. She'd flown over large tracts of the place, balancing on her gently flapping law books, and so far had seen no end. Students camped out in there for days, sometimes, near the exams.
Occasionally people even got lost in there, and River would sent out patrols of curious books, and when they found a student they would guide them back to the front desk, pushing and leading and flapping until the student would emerge, blinking, into the bright library light and be greeted with a warm smile and a kind 'hello, sweetie' from River. However, students had been trapped in the library for days before, the shelves refusing to budge, and once there was a student who went missing in the last week of a break and was not even noticed missing until a few days after their friends returned. Those unlucky students were also greeted by concerned friends and mugs of hot chocolate.
Come night time, River would fly on her books to a little clearing amidst the shelves, and she would lie on a hammock and drift off to sleep, surrounded by the soft rustling of ink-stained pages.
River loved her books, and the library was her home.