Yes, I've reread is the first 2/3rds of "Understanding Media" several times and never finished it, but would still highly recommend it. There is also some excellent old interview footage of him when he was a pop culture figure which is originally what fascinated me. For me it would have been hard to read his writing without having seen those interviews first -- he has a very distinct style of writing/talking and is interesting as an integrated person within recent history and not just a collection of ideas. On that note, I'd also recommend Videodrome.

edit: There are also more polemic anti-tech presentations of his ideas, especially by Neil Postman or Nicholas Carr which are good in their own way. But to me the fascinating thing about McLuhan himself is his dedication to presenting his views in a such a matter-of-fact way that most of his early followers were probably very antithetical to his personal beliefs.