Robert Letham, Union with Christ: In Scripture, History, and Theology 
(Phillipsburg, NJ: Presbyterian & Reformed, 2011), 123–28:
Ten Theses on Union with Christ and Transformation
- The union we enjoy with Christ is more real and more fundamental than the union we have with members of our own bodies. . . .
- This is not a union of essence—we do not cease to be human and become God or get merged into God like ingredients in an ontological soup. This is not apotheōsis. . . .
- We do not lose our personal individual identities in some universal, generic humanity. . . .
- Union with Christ comes to expression in, and is cultivated by, the Word and sacraments. . . .
- The body and blood of Christ are not materially, corporeally, or physically present in the Lord’s Supper. . . .
- In the Lord’s Supper we are lifted up by the Holy Spirit to feed on Christ. . . .
- We are not hypostatically united to the Son. . . .
- We are united with Christ’s person. . . .
- It is effected and developed by the Holy Spirit through faith, in and through the means of grace: the ministry of the Word, the sacraments, and prayer (WSC 88). . . .
- It will eventually lead to our being “like [Christ]” (1 John 3:1–2; see also Rom. 8:29–30; 2 Cor. 3:18), for “it is the intention of the gospel to make us sooner or later like God” (Calvin).
Related: Phil Gons has collected a helpful list of resources on union with Christ.
You should also know that Dr. Marcus Johnson, Assistant Prof of Theology at MBI, is writing a book on this subject (Crossway, 2012 or 2013). This was the subject of doctoral work in Toronto with particular emphasis on Calvin.
The Gaffin lectures on Uw/X are also quite helpful.