There are many different "canons" out there, most of us are familar with the Catholica dn protestant one, but there are others, some older, that have more books.
In the OT and NT there are "aprocrypha", ancient writings that are NOt part of the standard but are still quote in some passages of the "approved" OT and NT.
Typically some of the books are left out because the authorship is called into question, others because of the date, others because they are controversial and may go against the mainstream thought at the time of "canonization".
Most of these books are available to all so one is certianly able to judge for oneself their validity or lack there of.
Remember, Revelation was NOT part of the common canon for sometime.