Author unknown, this book is not named, but is one of the general epistles, written to Jewish believers and was probably named "Hebrews" (aka Exhortations) in the 2nd Century AD. The author states it is of few words (13 chapters is few?) and is designed to "lift you up", build you up and stir you up. It is authored during the lifetime of Timothy, so before 97 AD. And as there is no reference to the temple destruction, it was obviously written prior to 70 AD. Many ascribe it to Paul, but there's no proof.
Important verse: Hebrews 2:1 KEY VERSE: Hebrews 3:1