Drastic turns/one offs for classic characters
 

I'm not a huge classic comics guy, though I do read a lot of modern stuff (mostly not super hero stuff) but I have stumbled across a few TPBs that are really interesting, drastically different takes on classic characters. So far I've found:

Superman: Red Son - where superman is raised in the USSR instead of the USA
Hulk: The End - where the hulk's immortality leads him on an introspective journey after we've all killed ourselves in a nuclear war
Batman: The Dark Knight Returns - Miller's classic retake on Batman (not as out there as the other two, but still drastic and really good)

So what other books (preferably collected as TPBs) would you guys recommend to someone new to the superhero genre that are truly interesting, drastic re-takes of characters that I can look into?

loooking at the examples youve provided, are you talking about alternate universes?

Not specifically, because an alternate universe is just a way to set one continuity apart from another, when they contradict each other. I'm talking taking something completely fundamental to a character and changing it to tell an interesting store (ie: Red Son), or taking a philosophical look at a traditionally "strong man" character (the hulk one).

Just things that are completely out of left field but really work within themselves. Another example would the be the Transformers mini series where they arrived during the steamboat age instead of ours, so they turn into trains and ironclad ships, etc.

Actually, you *are* talking about alternate realities. All those examples are some of the best examples of alternate realities I can think of.
But it's more or less just arguing terminology. It's the all the same thing.

So on that note, I'd suggest:
Justice League: New Frontier- An alternate reality take on the formation of the Justice League. Set in the silver age, but with more modern story telling styles.

I would also suggest expanding your horizons to Self Contained stories. Stories that are "canon," and set in the mainstream universes, but really require nothing else to read them.
Batman: Hush- There's a new serial killer in town, and all the clues to his identity points to Jason Todd, the second Robin. Only he died in Batman's arms years before.
Identity Crisis- Someone is killing the loved ones of the various superheroes. Someone knows who they are. One of the best written stories of all time, IMO. And pretty damned heartwrenching in places.

Dc's Kingdom Come is a pretty good read for newer readers, although with the reboot all that is out the window.

And then theres the crazy as balls Earth/Universe/Paradise X books.

Read The Golden Age- a miniseries by DC for adults about the classic WWII heroes after the war ended and the paranoia of the cold war started.
An amazing read with the best realistic superhero comic art I think I've ever seen- written by James Robinson (Starman) and art by Paul Smith (too numerous to list).
http://d1466nnw0ex81e.cloudfront.net.../4452391_1.jpg

Really, it's just fantastic.

Iron Man: Haunted is amazing and SO well written and drawn- like the Golden Age, it takes superheroes and makes them believable in both looks and characterization. My favorite alltime IM story and he's my favorite alltime character!
http://media.comicvine.com/uploads/6...3-24_super.jpg

DC's alternate reality classic The Nail he is a must read as well- it's what happens when ma and pa Kent's truck runs over a nail, blows the tire and they never find the rocket with baby Superman in it. The DCU with no Superman, in other words. Great Alan Davis art.