Thanks for the comments. They were encouraging and I do enjoy hearing from other mothers.
Last night we swaddled Luke again- and I might mention that only his arms are swaddled. His feet get to kick about freely. He slept 8 and 1/2 hours straight! He must have been tired from the past few rough nights. Also, we put him to bed at 7:30 instead of 8:30, which the sleep book recommends. Establishing an earlier bed time was a good suggestion. I think in the past, Luke has been needing to go to sleep earlier, and I hadn't noticed.
In my last post, I did not mean to disparage the sleep book itself, but rather to say that my reading of it was the problem.