Read the series.
For my money the top three works in the list are indispensable. The next two are important to have. I do not think the warning passages in Hebrews have yet been tackled adequately (and who is up to the task?). I personally hold that Hebrews should be read alongside the Olivet Discourse.
1. Peter T. O’Brien – Yes, I know the author has gotten it in the neck for plagiarizing (but it is odd plagiarism, like repeating phrases, not exegesis). Because of this you’ll have to search for it at a decent price. But this is really very good.