There are a great many excellent commentaries on Hebrews.
Pride of place goes without a doubt to Owen’s seven volume Puritan commentary. What he doesn’t know about Hebrews, rabbinical works, and arguing that Jesus is the Messiah, isn’t worth knowing.
Second-rate (only because none can compare with Owen): Attridge, Brown, Ellingworth, Guthrie (NIVAC), Lane, Westcott, Pink, Hughes, France
Third-rate: Bruce, Guthrie (Tyndale), Koester, Long, Moffatt, Craddock, Hewitt, Buchanan, DeSilva, Luther
Forthcoming: Alexander (ICC), Allen (NAC), Carson (BECNT), Moo (ZEC), O’Brien (PNTC), Phillips (REC)
Conservative: Owen, Brown, Guthrie, Lane, Westcott, Pink, Hughes, Bruce, Guthrie, Craddock, Hewitt, Luther
Moderate: Attridge, Ellingworth, Koester, Long, Moffatt, Craddock, DeSilva
Of the forthcoming commentaries, all but Alexander will be conservative. I don’t know about Alexander, but the series is moderate to liberal.