Is there such a thing as a post-Crisis Superboy?
Yes and no, it can be a bit confusing.
Post-Crisis, Clark Kent/Kal-El did not adopt the "Super" name and costume until he was an adult. So in that sense, there is no such thing as a post-Crisis Superboy. However, as a teenager, he
did go around as a Super powered behind-the-scenes helper, so he was "kind of" a Superboy, just no name or costume. As far as I know, there have been very few tales of this era, perhaps just
Birthright which only covers the later pre-Superman years.
However, there is another post-Crisis character who uses the Superboy name. He was introduced back in the 1990s as an adolescent boy with Superpowers who was believed to be a clone of Superman and who was created by the Project (post-Crisis, now called the "Cadmus Project.") It was later revealed that he wasn't a clone of Superman, but of some other person (or people?) and who had powers introduced into his DNA by the Project when he was created. I'm really not sure of the details as I didn't follow it closely. So in that sense, yes there is a post-Crisis Superboy.
My favorite post-Crisis "Superboy" tales are:
1) The issue(s) where the post-Crisis Superboy meets the pre-Crisis Superboy:
(That was early on in his original title if I recall correctly. Can't remember if it was a lead-in to
Zero Hour, or to
Hypertension. Actually, didn't he appear twice? Maybe for both of these serieses.)
2) The
Jeph Loeb issue that was basically a big conversation between the post-Crisis Superboy and Superman:
.
Then, to add to the confusion, there was also a comic book tie-in series with the
Superboy TV show. This had to take place outside the newly established post-Crisis DCU, since in the new DCU, there never was a Clark-as-Superboy. Some of these issues are pretty good, with creators who had been thrown off the Superman titles for being "obselete" but were shuffled off to this obscure tie-in title with the low readership. People like Cary Bates and Curt Swan. My favorite issue of this series is
The Last Superboy because it ties in the superboy TV show continuity with the post-Crisis Byrne continuity, saying that there may not have been a Clark-as-Superboy in the DCU, but there
was one in Clark's imagination. So although the new DCU never had a Superboy, at least Superman himself fondly remembers those "Superboy" stories of his youth along with the rest of us.
There was also the Pocket Universe Superboy - but I'd better stop now, I think I feel another Crisis coming on.
Was Hypertension ever released as a TPB if not why not?!?
Sadly it hasn't been released. Not much of an overall demand for Superboy trades,..
That's because the stories aren't about Superman when he was a boy. If they were, there'd be a
lot of interest! It's time to bring back the young Clark/Kal as Superboy.