Ender's Game and Ender's Shadow are two very odd books, but easily in my tops. Definitely sci fi classics. In the same genre, Hyperion and its sequel are just off the wall and absolutely epic in scope. Lots of expert world building by Simmons, I really enjoyed those two although a lot of people think the sequel faltered a bit (it did, in some sense, but it was still excellent).
Haven't read much since I blazed through Martin's ASOIAF series though. Nothing really touches it as far as sheer readability, entertainment factor, and epic scope.
I prefer genre classics rather than so-called "literary masterpieces." In one of my first college level English courses, had to read some of these types of books, they included Lolita which was hot garbage pedophile poetry and some other "great novel" about some hicks in the south and it was told from different viewpoints. (I have since remembered the name, it was Faulkner's The Sound and the Fury) I blocked it out of my memory. Was torturous. I did read One Flew Over the Cuckoo's Nest in that class, though, which was very, very fun. I really enjoyed that. The Remains of the Day was another one, it was about a British butler who traversed the countryside or some shit. I don't remember a ton about it but I do remember it resonating with me, and I liked it. I may have to read that one again. It sounds super boring and I guess it sort of was, but...I dunno.
To me, the most IMPORTANT part of a good book (fiction, at least) is that it tells a damned good story. That's it. A good story, one that entertains and keeps me compelled to read. Now there are a bazillion factors that can make a story good, but you get the idea. I don't really care that much about artsy language or fancy writing style or anything of that sort. Obviously I don't want a book that looks like it was written by a 12 year old, but I'm all about good stories with characters I want to root for or root against and shocking moments and all that shit. I can appreciate advanced literary methods, however I don't like having to analyze every sentence to figure out what the fuck is being said (see: Lolita).
The Road and Blood Meridian, two books I think everyone should read.