Thanks for all the input. Here are the Dylan Cd's I already own.

Bob Dylan, Frewheelin', The Times They Are A Changin', Bringing It All Back Home, Highway 61 Revisited, Blonde On Blonde, Blood On The Tracks, Desire, The Basement Tapes, Empire Burlesque, MTV Unplugged, Time Out of Mind. Greatest Hits Volume 2

I had planned to buy in the next while: Another Side of, Oh Mercy, The Bootleg Series 1-3, The Bootleg Series 4 (Live Royal Albert's Hall)

Given this collection would I be stuck with a CD that I already would have most of the material? I'm especially concerned that some of the stuff on Biograph may also be on the Bootleg series.