Our Rick Steves tour only gave info for taxi and bus from CDG to our hotel near Gare de Lyon. There is a train too...any ideas why it wasn't also suggested ? Are the distances between train and metro too long?
Beats me. There's no metro involved. It's RER the whole way with a switch from B to A at Chatelet. I hate the station because of its size, but in this case the tracks are close together.
Air France bus #4 will take you directly from CDG to Gare de Lyon. Price is 16.50 euros. Much easier than the RER if you're hauling luggage IMO. Much cheaper than a taxi. Info here: http://www.lescarsairfrance.com/en.html
In my post on your earlier thread on this subject I suggested that you take the RER B to Gare du Nord and the RER D from there to Gare de Lyon. Doing it that way means you don't have to transfer at Chatelet-Les Halles. As to why the RS tour doesn't include the RER, I'm guessing they limited their suggestions to direct routes: Air France bus, shuttle, or taxi.