Posts: 968 From: Staten Island, New York USA Registered: Nov 2007
posted 07-10-2015 08:41 AM
I think the first one (SP-400) is more of a 'coffee table' type book with a lot of color photos and general information covering all three manned missions (similar to those glossy booklets NASA put out after each Apollo mission), while the second delves into the complete technical (and political) history back when it was known as Apollo Applications thru its reentry from orbit.
At almost twice the chapters of the other book, SP-4208 also has appendices and source notes so you can consider it more 'scholarly.' There was also the publication 'Skylab: A Chronology' (SP-4011, 1977) and also ones covering Earth photography and solar observations.