What Is It With Open Endings?

I have just finished 'The Glass Books Of The Dream Eaters' by G. W. Dahlquist (and my essay, by the way, yay for me!), which is a really good book (although hard to read in bed because it is about 750 pages and a hardback book with a stuck-on dust cover) filled with intrigue and exciting stuff happening (as well as a lot of sex which I did not expect). It is also immensely hyped up, with the book designed to look like the Glass Books of the title, and lots of 'mysteriousness' surrounding the author, but that is not as annoying as the fact that for some stupid reason, the author thought it a good idea to give the book an open ending.
I mean, seriously, if you can think of all the amazing and fantastical things that happen throughout the book, you can come up with a simultaneously satisfying and original ending! Is it really too much to ask to know what happens to our heroes after they have successfully done away with the baddies (it is a 19th-century style novel, so you know they baddies are gonna get it)? I don't want them to successfully end their mission only to then be left in a lurch! And it is not like the author would have any problems coming up with something good; the whole book was pretty full of surprises and clever distractions, so a good (meaning, Merel-satisfying) ending could also have been constructed.
I am highly pissed off about this, I really am. I mean, it is not as bad as the end of Sue Townsend's 'The Queen And I' (for which quite frankly, she should be shot), but still...
Maybe I am just too simple-minded to appreciate the satisfaction of not really knowing for sure, but I really would have preferred it all to be neatly tied up. And I was so proud of Dahlquist for not giving the book one of those stupid 'this is where the villain explains his entire evil plot to the goodies while giving them enough time to regain their strength and kill them before the evil plan is set in work' scenes...
Anyways, I would write a really intelligent and in-depth post about this (because I could, you know! Don't think I couldn't!!), but I have spent all my intelligence on my essay, which is probably the way it should be. Still, BLEGH! to mister Dahlquist for not giving me a simple (or complicated, really, I am easy that way) and satisfactory conclusion for Celeste, Cardinal Chang and Dr Svenson (I don't really care about Eloise, she can drown for all I care).
And he'd better not done it so he could make a sequel, because that would really tick me off!!