Song of Songs: Though not strictly a commentary, Stephen M Clark’s As Good As It Gets is magnificent – deals with the book as a collage of love poems, giving wonderful perspectives on human relationships, and at the same time relating it all to our relationship with Christ, with poems, Psalms and prayers thrown in.
Hosea: Douglas Stuart’s Hosea-Jonah – brilliant; see below under Amos for more.
Amos: Douglas Stuart’s treatment in his Hosea-Jonah, volume 31 in the Word Biblical Commentary series. Don’t skip the introduction, pages 283-295 – he is well-informed, insightful and a superb (clear and easy-to-read) teacher. This is not a light, entry-level commentary, yet perfectly accessible to any serious reader with some time to spend.
Matthew: RT France’s big commentary in the NICNT series is far and away the best thing on this gospel for the serious reader with some time to spend. Quite magnificent, original without being quirky, and a delight to read.
Now we are God's children 