Interestingly, your copy may, as mine does, contain a brief section on The Time Between The Testaments. In it there is brief section on the Apocrypha and its exclusion. If you have the time, read it next to a Catholic defense of the inclusion of those books. The arguments of the former don’t hold water. My two favorites are: “There is no clear evidence that Jesus or the Apostles quoted any Apocryphal works as Scripture” which is entirely untrue and were it used as the standard would cause us to throw away any number of OT Books, and “the Jewish community which produced them repudiated them.” Well, we Christians wouldn’t want to go accepting things (or individuals) produced by the Jewish community but later repudiated by them, would we?
As for teachings in the Apocrypha, the NIV says they can either be found in “canonical” Scipture or run counter to it (or rather their interpretation of it). Among such teachings are Prayers for the Dead and Purgatory (2 Maccabees 44-46) and Intercessory Prayer (Tobit 12:12). As far as I understand, there are numerous others, particularly in Sirach and Wisdom, that bolster Catholic teaching.