At moments brilliant but mostly drug addled crap, Mexico City Blues is Jack Kerouac's career in microcosm. There are times when his poetry and prose are truly great, when he can incite or captivate or evoke a sensation like a master, but most of the time he is a hack. 
 I know, I know, y'all love him and think he is a literary god, but he really isn't. He and his friends (he is no Ginsberg or Ferlengetti, after all) came at a moment when they could do anything they wanted with no worries about editors or quality. In some moments and in some cases this was a boon, but it was not always so, and Kerouac's ouevre is too littered with the latter for him to be truly great. Read Mexico City blues and you'll see what I mean. 
 (p.s. it's more fun to read in French.)