The on-line Free Dictionary (idioms) explains the idiom as:

"To do something in the way someone else would do it; to behave or act like someone else." For example in a sentence:

You are looking particularly fit and healthy these days. I think I'll take a leaf out of your book and go running in the mornings.

The Macmillan Dictionary uses the following example:

"They should take a leaf out of industry’s book and pay both management and staff on results."

The English language is full of idioms - some specific to certain cultures and languages. Others common to all.

More Info: www.macmillandictionary.com