What is the name of the book that you decrypted?? A file "2d79ba25.bin" was encrypted using AES in CTR mode using the same key and the same IV. In this case you also want to crack your file. But in this case there is no known plaintext, so you must do a COA attack.

Here are a couple of hints.

What happens when you XOR the code for an alphabetical letter with the code for "space" in the ASCII standard?

Can you think of a way to find the locations of all the spaces in all of the files?

If you know where all the spaces are, how can you use this to find the keystream?

Using the keystream, how can you decrypt your target? Please code?