I would read them in that order. The endings are nice and complimentary too. I think McCarthy read Lebowitz and took some inspiration. Lebowitz is also a good palette cleanser after the tender bleakness of the Road. Intellectually stimulating and different enough while in my mind being a non cannon sequel to the Road. Love both books so much. Good little post apocalypse pairing
Interesting… I read both recently, and enjoyed them. Never thought of them as being a pair though – both are great books though.