Question: In Suruga Monkey Part 2 of Bakemonogatari, Kanbaru's room is literally full of red hardcover books. Why is this and what does it represent?

Answer: 
That's her massive collection of BL (boys' love) books (which she is also into, besides considering herself a lesbian), at least that's what they represent. As many other things in Monogatari's animation, it should be taken more symbolically than literally. Take for example Senjougahara's "arsenal" of stationery in episode 1 of Bakemonogatari, or even more obviously the constantly shifting, multiplying, growing, falling etc. pile of pencils in episode 6 of Nisemonogatari (you'll know when you get there :) ).
I believe the books (which are from BL) can represent the mental state of the character, who is also homosexual. Maybe that's why it's all a mess, and when Araragi goes to Suruga's house during a long conversation, they arrange (literally and metaphorically) her books (feelings). Perhaps this is why, in the Nisemonogatari tidying scene, when Suruga gets confused in the conversation, the books fall into a domino effect, and when Araragi helps Suruga to find herself again, the books arrange themselves. But that's just my interpretation