I like the following outline because it uses scriptural phrases from the book itself.
Chapter 1 - 4 : "Thou art My Son" 1:5 - The Pre-eminence of the Son
Chapter 5 - 8 : "Thou art a Priest" 5:6 - The Priesthood of the Sovereign
Chapter 9 - 10 : "This is the Blood" 9:20 - The Propitiation by the Sacrifice
Chapter 11 - 13 : "These all, having obtained a Good Report" 11:39 - The Pattern of the Saints