For me, it has to be Tribulations by Ken Shufeldt.
The hero, Billy, is 'accidentally' injected with DNA from a mummy when he is an infant. This DNA somehow turns him into some kind of super-genius. When he is an adult, he manages to evacuate several thousand people from Earth before an asteroid strike destroys the planet. Once in space with a fleet of interstellar ships he built almost singlehandedly, he manages to convert his own ship into a FTL ship, although we are not told how he did it, other than that he had "giant coils" mounted to the front of the ship while it was being constructed because he had an "idea that they may be useful someday". This all happened in about the first ten pages or so.
I can deal with juvenile story-telling and no character development if the plot and science are good. But even these are absent. I'm not going to get into the plot, in case someone may want to read this book. But the science is horrible.
It is never explained why a genius who could build all these interstellar ships and put together a warp drive from fishing line, duct tape, and some copper coils had no ideas on how to deflect the asteroid from its course.
When they first leave the orbit of the destroyed Earth, they have some argument over which galaxy they should travel to in search of their new home. Why wouldn't something in the Milky Way do?
They finally decide to go to some unnamed dwarf galaxy, and Billy is all twisted up because that galaxy is four light years away.
Billy decides to invent his hyperdrive because his ships, which cruise at 1/3 light speed, would take centuries to reach the dwarf galaxy four light years away.
Again, all that science is in the first ten or twenty pages. There is much, much more where that came from.
The book was published by Tor, and I know they don't have a reputation for producing the highest quality stuff, but I really don't see how this stuff could get past any editor. This is elementary school science. I would have probably enjoyed this book when I was in second or third grade, but it's marketed to adults.
I just want my seven dollars back.
EDIT: By the way, I could only make it about a third of the way through the book. I just skimmed the rest. I bought this when my wife was in Germany and it was supposed to occupy a Saturday night for me. That might be part of the reason I feel cheated.