Hm. Well. I have mentioned these before in other threads but your purpose is a little different so I shall lean towards that direction in this post. Apologies if either recommendation has already come under your radar from the previous discussions here on the Glade.
For the most part, I will recommend Brandon Sanderson to suit these purposes. Though he has begun an epic fantasy series to match things like the Wheel of Time, most of his work is on the short and easily digestible side. His longest cohesive story arc is a trilogy, which while very long for your purposes, still says something about the role he can play here. I'd say he's also very strong at drawing you into the story, because all his worlds have some twist to them, usually central to them, and he hits the reader with it hard, early, and often. He seems to put a lot of time into the very first line of each book, in fact. :p He just released a novella, set in modern day, but I haven't had time to read it... still, if he catches your fancy, that would be another potential option for short and easy reads.
Best part for your purposes is that one of his standalone novels is available for free in .pdf form, so you can read a chapter or three with an hour or less investment. Though I don't think it's his best work, it
does have one of the characters I find most enjoyable to read out of any books I have read. Here is the link:
http://www.brandonsanderson.com/drafts/ ... 1st_ed.pdfI will also mention The Dresden Files, which has got a fair bit of mention here over the past year or two. It is a very long (and far from complete) series, so I didn't want to even mention it at first, but upon reflection they are very easy to read and the pace is always pretty fast and varied. Definitely the most fun books I've read in awhile, if not ever. It does take a few books before the series gets to be quality, I would say, as the first few are sort of shallow fun... but man, some of the later books have been surprisingly deep. So eager to get the next one! Just a few months longer...
edit: In the case of Warbreaker, which is the free .pdf book, I vote the opening line of Chapter 3 (page 44) as the typical Brandon Sanderson first line with a twist. Technically not the first line of the book, but the first for that character has to count for something!