A favorite phrase in the New Testament is "how much more...," using a comparative analogy to describe God: "If you then, who are evil, know how to give good gifts to your children, how much more will your Father in heaven give good things to those who ask him!" (Matt 7:11) This comparison lies behind many of the parables as well: if a father would forgive his prodigal son, for example, how much more will God forgive us? The Letter to the Hebrews strikes me as one long argument of "how much more": how much more wonderful is the sacrifice of Christ compared to the sacrifices of the Temple, how much more wonderful is our relationship to God in Christ than it was before Christ came. The unknown author – not Paul, despite the closing greetings – is addressing himself to his Jewish contemporaries, and thus the comparison is explored with great depth. I confess to a good bit of discomfort with this comparative/competitive approach - it seems important, then, to read it in the context of what was then a relatively tiny group of "Christians" trying to convince contemporary Jews of the value of their understanding of what they believed.
I've also never been comfortable with the theology of atonement, of Jesus atoning for the sins of humanity through his death and resurrection, not because I don't agree with it (or at least with my understanding of it!), but because the language and imagery can become confusing and end up sounding quite brutal. If Jesus must die to make up for how awful we are in order to satisfy a God angry at our awfulness, that just sounds appalling to me – because it sounds like one human life being forced to suffer for everyone else. But if we remember that Jesus is God incarnate ("the exact imprint of God's very being," Hebrews 1:3), then we are talking not about needing to have a human die to make God satisfied, but God himself dying in human form to show us the depth of his forgiveness of our sins and thus of his love for us. I think it will help enormously in reading the arguments laid out in the first two thirds of Hebrews to keep this perspective in mind.
For this is another letter that has a great finish, whose arguments lead to powerful messages of hope. The confidence offered us in 10:19-25; the celebration of faith in chapter 11 ("faith is the assurance of things hoped for, the conviction of things not seen"); the glorious vision of the support of a community of faith in chapter 12 ("Therefore, since we are surrounded by so great a cloud of witnesses...let us run with perseverance the race that is set before us") - these are all renowned and moving passages. But the real big finish is the passage we use as the final blessing after communion during the Easter season: "Now the God of peace, that brought again from the dead our Lord Jesus, that great shepherd of the sheep, through the blood of the everlasting covenant, make you perfect in every good work to do his will, working in you that which is well pleasing in his sight...," (13:20-21, King James Version) to which we then add the Trinitarian blessing. To pray to be perfected, completed, by God in Christ is to seek a blessing indeed.