I read IJ in the late '90s after two aborted attempts. I kept thinking about the parts that I HAD read the first two times and finally read it all the way through in '98-'99.
Then I read these two essays
1)
http://dfan.org/jest.txt (by Dan Schmidt, about 4 pages)
2)
http://www.geocities.com/Athens/Acropol ... hesisb.htm (by Chris Hager, about 25 pages).
Then I read IJ again sometime in 2003-04. In the last few weeks, I reread A Supposedly Fun Thing and Consider The Lobster and started IJ again, meandering through the first 100 pages so far...
I was getting this uncomfortable feeling regarding all the SPOILER concern on this site and couldn't really articulate what it was that was bothering me...
Here it is - the book is non-linear. I think this is pretty clear. Therefore, I honestly believe that spoilers don't matter. You could read the book the backwards, and I really don't think it would impede your enjoyment or understanding...