The Elements of New Testament Greek

Absolutely excellent! I couldn't recommend it more.
I've been going through it in my lunch hours at work and after 5 months I'm into chapter 8, I know some 140 Greek words which combine with the paradigms to mean I can read around 1,500 words, and I have taken my Greek New Testament to church and been able to read roughly half of the text during sermons!

Since 1914, C.U.P. has published The Elements of New Testament Greek, a best-selling textbook for scholars and students of the Bible. The original work by H.P.V. Nunn was succeeded in 1965 by J.W. Wenham's book of the same title and Jeremy Duff's new edition advances a long-established tradition into the twenty-first century. Lessons are organized so the most important aspects of Greek are learned as well as the most commonly occurring words in the New Testament. Hundreds of examples cover every book of the N.T. and almost every chapter includes a passage to translate from it. A vocabulary audio CD is also available separately.

Very concentrated and requires tutor help to work through so would not recommend as a "teach yourself".
Also print is rather small and the breathings are not clear without a magnifying glass.