When I asked about fake books one of my musically knowledgeable co-workers said "a lot of people only read chords".
For the rest of us though a fake book is a type of musical score/sheet music collection:
Each song in a fake book contains the melody line, basic chords and sometimes lyrics - the minimal information needed by a musician to make an impromptu arrangement of a song, or "fake it." The fake book is a central part of the culture of playing music in public, especially in jazz, where improvisation is particularly valued.
I had an "aha" moment at the phrase "public playing". I was reminded of piano bars with huge brandy snifters full of dollar bills (I'm old) sitting atop the piano where a suave, well dressed man - or woman- played requests for tips. Occasionally, through the smoke and dim lights, you would see a song request stump the musician and out would come a loose bound collection of lead sheets songs - their personal fake book.
Nowadays, I sometimes get people who look a bit down-at-the-heels asking for fake books. Out of curiosity, I asked one man what he used the fake book for and he explained he was a street musician expanding his repertoire.
If you're interested in fake books you may enjoy some of the following ones available at Toronto Public Library. The biggest collection of sheet music (over 30,000 scores!) is found in the Arts Department of the Toronto Reference Library. We have scores to borrow or for use only in the Library (we have copiers).
There are also come online resources you may find useful: