For technical books, I agree it is possible to skim rather quickly through stuff that I already know with speed reading approach.
My own assumptions are quite different, namely I expect that like most other pleasurable activities, you get the pleasure from the time spent doing it, but that doing more of it.
For example, if two people both spend 5 hours hiking, and one person hikes 10 miles and the other 15 miles, I wouldn't then assume the latter had gotten more enjoyment from his or her hiking. Nor would I assume someone that had eaten a meal with 1000 calories got more enjoyment than someone who had merely eaten 500 calories.
This is a question I always ask all speed readers and the answers are always so muddled. I can never understand what they are getting at.
Perhaps I relish a good novel more than most, but to me the idea of speed reading a good novel sounds about as appealing as speed drinking a fine wine.
You may be underestimating how many people do this as well :P
Personally, I would love anything that got me thru books faster. I've been reading A Scanner Darkly for months. Admittedly it's more of a problem of concentration than reading speed, but I do understand the appeal of reading quickly. You'll simply get thru more books.
That being said - I don't understand people who listen to sped up podcasts, as I hate burning thru my favourites before a new episode is out. So I think it's just down to personal preference.
If I am enjoying a book, I can’t imagine having the urge to finish it faster. Or slower. What could possibly be gained?
Edit: also, just some unsolicited thoughts on your struggle to complete a Scanner Darkly. IIRC, A Scanner Darkly is a fairly average length novel, meaning you might expect to finish it in ~10 hours of reading. My personal experience is that it's best to enjoy a novel within a relatively limited time frame (say a couple of weeks) so that the various characters and plot lines stay fresh in your head.
If I were in your situation, I would probably question whether:
A) If I actually like the book. If you are even a quarter of the way through a book and don't like it, nothing wrong with picking up something else. As I mention above, books are for enjoyment. If you don't enjoy it, what's the point?
B) If I perhaps don't have time to read a novel now. Sure, nothing wrong with starting a movie, pausing for dinner and then finishing it afterwards. But there are limits. You wouldn't want to split a 2 hour film into a dozen ten-minute segments. And I would argue, wouldn't you want to split a 10 hour novel into a 60 ten-minute segments either. Just not a good reading experience. Nothing wrong with putting the book on hold and coming back in a few weeks once your schedule has calmed a little.
My business sense tells me there's a potential market for speed hearing here.
Also, I can see how if you have multiple hobbies/kids/etc you'd want to speed up your reading because you have limited time.