The clue to decrypting this note is written on the back of the note ("They say you shouldn’t skip the boring parts of a book, but rules were meant to be broken.")

Pay attention to the underlined words.

The words book and skip are underlined. One of these words relates to the cipher type and the other relates to a piece of physical evidence you need to decrypt the message.

This is a skip cipher. Once you've figured out the key, you'll only read certain letters and skip the rest. For example, if the key is 3, read every 3rd letter.

Examine the bookmark carefully.

This is a skip cipher with a key of 4. Read every 4th letter.

The clue to decrypting this note was the reference to the word "book" (at the top of the note). There is a bookmark with the number 4 written on it. Read every 4th letter in the note and skip the rest.

Decrypted, the note reads:

caught tiana lurking near iguana enclosure said she forgot something but panicked when she saw me

rachel dropped a green pouch yesterday and freaked out when i tried to pick it up

somethings off five transfers after hours this month with untagged animals and new handlers devens always there but he doesnt even work nights

i confronted a handler and someone was watching me from the bushes they dropped a hair clip