The original Roswell books 1-10 are out on the web for all to read, as are some of the books based off the show including: pursuit, nightscape etc.
You can find them here:
http://www.wattpad.com/stories/search/roswell
And someone actually wrote a fanfic based off of the books which I loved. It was pleasantly on the same level as the books which is probably why it appealed to me. I loved it. It tied up loose ends and it GAVE Michael/Maria that final happy ending that we only got fleeting moments of in books 1-10 . I consider it book 11 because it truly is like the books...except with more featured friendship which at the end of book 10, I think EVERYONE was craving...well at least for M/M.
It is called: "New Understandings" by Beowulf which you can find here:
http://www.crashdown.com/fanfic/afterhr ... lfMM.shtml
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As far as the books go...they are nothing like the show, except for the couplings. But even in that...Alex and Isabel don't get together, though he is alive in the end. Actually he got trapped on Max's home planet and they had open up a worm hole to save him. They're worth a read if you like Roswell...just to give you a history of how our Roswell came to be. And they do have some interesting bits that I wish were incorporated into the show like the dream orbs.
I didn't particularly like the books mainly because I was excepting so much more, but then realized that they were written on a middle school level and I wouldn't be getting the depth I wanted and was use to. The books based off the series are much better, but plagued with grammatical errors that it shames me.