Basically, Hebrews was written toward those practicing the Jewish faith. Jesus had broken paradigm after paradigm of the Jewish faith and those in the early church were walking in His footsteps. Especially since I visited Israel and Jerusalem just about a year ago, I have been fascinated by just how revolitionary Jesus' teachings were. He was really "rocking the world" of the Jews. Hebrews 1 starts off with no holds barred. Right from the start, it is announcing the change that took place with Jesus' presence here on earth. Prior to Jesus, God spoke to us through angels and prophets. But then He came here Himself, though His son, for the purpose of making a direct connection with us, leaving the power of the Holy Spirit to help in the accomplishment of that. Verses 10 through 12 then point out that the only thing of lasting power, of lasting worth, of eternal importance is one's relationship with God through the Son. Again, this was a revolutionary and difficult-to-accept nconcept for the Jews who had always placed their emphasis on ritual, specific acts of piety, and liturgy. Hebrews is telling us that those things would all eventually blow away in this world, leaving God and His presence as the one unchanging thing.
I am looking forward to the rest of Hebrews.