Essentially, An Introduction to Junior Wells is an abbreviated version of the Fuel 2000 release Calling All Blues.
This material predates Hoodoo Man Blues, the landmark 1965 electric Chicago blues album on Delmark with tunes recorded between 1957 and 1961.
Of the 14 cuts, nine were originally issued on Chief, with one track, "Little by Little," released on Profile.
The remaining bonus tracks are unspecified live versions of "Help Me," "Look Over Yonder," "Messin' with the Kid," and "I Can't Help Myself." All of this material is rock-solid and should definitely exist in your collection between Blues Hit Big Town and Hoodoo Man Blues.