The 1992 Explanatory Supplement has, unfortunately, many errors and typos. Be very careful using any data from it. Look up the published errata online, and if you can, look up the original sources also, as all of the errors are not in the errata!
Other than that, it is the definitive source, and the references alone are a goldmine of information. If you are really deep into astronomical ephemerides, you should get a copy of the 1961 Supplement also. It goes deeper into the trig math, and doesn't use a lot of vector math like the 1992 version.