Matthew Page asks, "Where would you advise someone to start with Goulder?" Interesting question. In his hey-day, there's no question but I'd encourage someone to get to hear him live. I used to attend his day schools here in Birmingham when I was a student and watch him spar with the top scholars of the day, watching him win every time. (Michael did tend to see the sessions in terms of "winning" or not.) He told me once that he thought Richard Bauckham had proved a formidable opponent and that, because he (Michael) did not have a good response to Bauckham on the Ascension of Isaiah, that the result was a "draw".
But since his retirement in 1994, to get a flavour you need to begin with his writings. On the whole, Goulder has written for an academic audience, aiming at peers -- fellow scholars and post-graduate students, and taking for granted much of the introductory material. He's rarely been someone whose written work one can approach as a beginner. The major exception to this would be his Tale of Two Missions (London: SCM, 1994) [published in the US as Peter vs. Paul] which is an enjoyable paperback introduction to one of his later theories on Christian origins. So that might be a reasonable place to start. But it doesn't get to the heart of what I've most enjoyed about Michael Goulder's work. I think the book I most like is Midrash and Lection in Matthew (London: SPCK, 1974), brilliant, imaginative, under-rated. Perhaps next I'd list Luke: A New Paradigm (JSNTSup, 20; Sheffield: Sheffield Academic Press, 1989). I've made one of his articles available on the web, "Is Q a Juggernaut?".