"Side Tracks" features all of the outakes on "Biograph" plus a few additional singles that have only been released on CD on greatest hits compilations, so that's why I recommended it. Covers just about all the loose ends in Bob's discography. You don't get all the redundant tracks you'd get on "Biograph" (though I actually quite like the track order of "Biograph" as is).

The CD version of "Side Tracks" is a Japanese import, though, so perhaps it'd be easier for you to pick up the more-readily-available-in-the-states "Biograph."