^I used to read as a passenger as well... Then I started to get car sick from reading and the way my Dad drives. I can still usually read on a long interstate road trip, but anytime we're driving in the city, all of the starting and stopping makes me queasy.
In response to the main thread, I can relate somewhat to your situation.
I love to read and it's not a boring experience for me, but I tend to only enjoy reading (or doing anything for that matter) if it's something that peaks my immediate interest when I have the time to read. As a result, there are lot of books that I would LIKE to read, but rarely do I pick them up and am in the mood to read them.
It's odd, but I feel like if I'm not in the mood to read something, I don't want to negatively impact the experience by reading it with a bias if you will. But on those rare occasions when I am in the mood, I plow right through it and if I like it and it's a series I'll have no problem continuing to read on in the future.
I've got "American Gods" by Neil Gaiman sitting on my shelf right now waiting to be read, but I haven't found the right time to start it.
Since I borrowed it from a friend (we're notorious for long book lends) it's ok and I can take my time, but since I first received the book, I've read at least 4 Star Trek books and that's because even though I WANT to read American Gods, I really want to read Star Trek.
Maybe that's part of it for you? Maybe you've got an established interest in Star Trek literature and as a result you can read it fairly well, but not having the same interest in the particulars of a sci-fi universe say for a more classic work like Frank Herbert's "Dune" it's harder to read.
Also, I'd say, don't feel pressure to read, the worst times I ever had reading something where I swear to God it felt like pulling teeth was when I either just HAD to read something because it was so good (Generally the problem I have with Classics - You're expected to like them in a sense) or with being assigned to read something for a class (like summer reading.)
Never fails, you tell me to read something and submit a report in 6 weeks, I'll show you a book that hasn't been flipped past page 17 until just about the night before it's due.