This is from my Amazon review of Edmund Clowney's The Message of I Peter: The Way of the Cross in The Bible Speaks Today series.
Clowney gives a straightforward and helpful exposition of this significant epistle. This series is highly readable, and Clowney's contribution on I Peter is no different. He has clearly thought long and hard about most of what he says, even if some of the argumentation for his views is left out of the book.
For a more serious exegetical commentary, look to Paul Achtemeier's Hermeneia volume, J. Ramsay Michaels' work in the Word Biblical Commentary series, or Peter Davids' NIC volume. I probably would agree more with Clowney's conclusions than any of Achtemeier, Michaels, or Davids, but the reality is that he's giving more of an exposition without always giving the scholarly details to back up those conclusions. When he does give arguments, they're often not detailed enough for someone who can handle the more detailed commentaries to be satisfied with. So even if I'm attracted by his conclusions, I can't always see how to respond to the others' arguments at the level they're dealing with.
For a more expository commentary, though, this book stands with I. Howard Marshall's IVP New Testament Commentary as the best you can find. Marshall has more of a scholarly bent, and his footnotes contain much information that Clowney either leaves out or works into the text, which makes Clowney's work a little more uneven. Sometimes he devotes much attention to an issue (e.g. his excellent treatment of the spirits in prison passage, encapsulating some of the material and arguments Wayne Grudem presents in his excellent appendix on the topic in his Tyndale commentary, but Clowney does so in a more shorter and more readable manner).
Other subjects get shorter shrift, and you would need a more in-depth commentary to get more background on those. Marshall seems to give a little more depth to more issues with some exegetical help in the footnotes and for that reason may be more helpful to someone who asks questions about that sort of thing. But I enjoyed Clowney more out of the two and got more out of his work personally. As straightforward exposition, this is great work. I skimmed through it in a day or two, paying closer attention to certain passages and moving quickly through others. Someone reading it more carefully would undoubtedly take longer, but it should be fairly light reading as commentaries go, and Clowney's eye is always to taking the biblical text into our contemporary setting, which increases the sense of relevance and immediacy of what Peter was writing about, making the read all the more enjoyable.