Lonesome EJ - A "fake" book is an anthology of common tunes, or sometimes songs, that has a straight-forward, simple melody and/or tab lines. I think the idea is for people to be able to "fake" their way through a tune if they don't have an arrangement of it.

There is an excellent set of Fake books, by Oak I think, for fiddle, mandolin, guitar, and banjo that lay out a lot of standard fiddle, old timey, and bluegrass tunes that are fairly well known.

There are also fake books for jazz and blues, I believe.