I'm going to have to pick up some of his solo work. looks like CD's of his 1st two solo albums are available on Amazon. Those 1st two albums are available on a two-record vinyl double album - but I don't think that double album is available on CD. one of the tribute compliations is also available on Amazon.
bottom line - the guy was really highly respected and loved in the music community. the article notes that Bruce Springsteen was being interviewed, and mentioned Slim's albums as something he was listening to.
also sounds like he helped hold the 'Mats together in the final years.