It is a mystery who authored this great book, humanly speaking. It is entirely possible that it is the work of Paul. But some other candidates are Barnabas, Apollos, Silas, Aquila, and even Clement of Rome.
Clearly the theme of Hebrews is the surpassing greatness of Christ, his superiority, and thus that of Christianity to the Old Testament system. The writer declares that Christ is superior in at least five ways (as the Son): He is superior 1) to the Old Testament prophets, 2) to angels, 3) to Moses, 4) to Joshua, and 5) to Aaron’s priest hood. Chapter one strongly declares the deity of Christ, but chapter eleven has been called “Faith’s Hall of Fame”. Hebrews 11:1 offers a surprisingly succinct description of faith, and what follows is a list and description of many of God’s saints, and how they lived out faith.
Here is an abbreviated outline of Hebrews:
I. The superiority of Christ to Old Covenant Leaders (1:1-7:28)
II. The superior sacrificial work of Christ as High Priest (chapters 8-10)
III. Final plea for persevering faith (chapters 11-12)