I'm not advocating the use of books as doorstops or following the design trend of using them for table legs. Unless, I suppose, that you're a fan of the game Jenga®, and you are willing to shift some of these hefty tomes around when you want to revisit a favorite.
Outside of classics like War and Peace and some mainstream literary fiction, Speculative Fiction has the greater percentage of bookshelf bending texts. This is based on researching standard word lengths of genres, and also how many of the books can fit on our shelves. No, SF can’t claim the longest books unless you count Mission Earth as one long novel as found on this 2009 list of longest books written in the English language (based on word count, not page count).
However, let’s take some recent examples like Sanderson’s Way of Kings and Martin’s upcoming Dance of Dragons and you see what I mean. Big worlds mean big stories, and even spread across multiple books the individual installments are enormous. Rothfuss’s Kingkiller Chronicles scratch at the 1,000 page mark themselves, with the latest The Wise Man’s Fear coming in at 993 pages.
While I find lengthy books really appealing, even if they could cause serious damage to my feet if I drop them, is it also likely they are daunting to some readers? Tell me; what is your reaction to weighty (literally) works of SF? Does finding out a book is near 1000 pages long increase your anticipation to read it or turn you away?