The tree has a large beehive hanging from a branch, a candlestick sign on the front door (sometimes an actual candlestick figure, depending on individual animation errors), a sign of an open book outside the door, and two balconies, one of which has a telescope.
In Friendship is Magic, part 1, Princess Celestia sends Twilight to Ponyville to supervise the Summer Sun Celebration preparations. She was supposed to stay in the library during her stay in Ponyville. The library is protected from lightning by a magical lightning rod as mentioned by Twilight in Look Before You Sleep. During the thunderstorm, Twilight has a slumber party with Applejack and Rarity and during the end of the episode, a tree falls into the bedroom through the window. In Swarm of the Century, Twilight wakes up in the morning to find the library infested with parasprites. In Sonic Rainboom, Rainbow Dash crashes into the library and knocks all the books off the shelves, making Rarity, Twilight, Pinkie Pie and Applejack organize them again.
Season twoThe Cutie Pox, Twilight pulls out a book called Perplexing Pony Plagues to diagnose Apple Bloom's case of "Cutie Pox".
In The Crystal Empire - Part 1, Twilight magically rips the entire tree out of the ground, exposing its roots. When Twilight and Spike are searching for a way to eradicate the Pinkie Pie clones in Too Many Pinkie Pies, Spike discovers a horseshoe-shaped button hidden in the back of a bookshelf. Upon pressing it, a secret compartment containing the desired book is revealed.
In Princess Twilight Sparkle - Part 1, Rarity mentions that after the Summer Sun Celebration, she and Twilight have a meeting schedule to redecorate Twilight's Loft now that she's a princess. As of Castle Mane-ia, it remains the home of Princess Twilight.