Pretty common. My sister in law is an athiest Jew, her parents seem to have zero interest in discussings things of God, the D&D kid's parents seem to be into theism and social Jewishness. I met a jew at the movie rental store a couple of years ago that was obviously a flaming homo. I have yet to meet a Jew that was series about anything about being a Jew.
Series, eh? Well, to shed some light on the situation - there are two possible sides to a Jew. One is religious. One is cultural. They are, as you are aware, not always apparent in one Jew. In fact, you can find some Ultra-Orthodox Jews that are virulently anti-Israel (and LIVE in Israel!!). You can also find some athiest or agnostic Jews that are extremely pro-Israel. I wanted to point out, however, that there are many Jews that have a good portion of both in them. You fill find many that many Jews here at FR fit that bill. Is that what you mean by a serious Jew?