My only criticism is that I felt that Spinrad used a convoluted sentence structure much of the time, that coupled with frequent use of arcane words really did make this novel a chore to read, at least for me. Overall though, well worth reading.
Is this a classic? Not sure. It must be around 20 years old now, and certainly when first released it was regarded as prime new wave material - advetised in *Omni* no less! But of course age doesn't make it a classic.
It's certainly original: I can't think of any other tale in the genre predicated on starships propelled across space by the power of orgasm. But that doesn't mean this is a sex fantasy either. Spinrad makes the idea work, and casts the captain of his ship into a credible (at least within this premise) dilemma, and eventually a real bind ... with a very new wave lack-of-ending to boot.
The genre may have moved on from the needs to break through barriers of editorial conservatism that - in part - inspired books like this. In some ways 'The Void Captain's Tale' will seem terribly dated, and I have to say that I think other wirters have since tackled broadly similar ideas and one it better. So this re-release may be of more interest to people who are bona-fide fans of 70's sci-fi than to the general reader.
But if you want some idea of where the genre has come from, it's worth a look.