If you want to stick with Batman, you may want to hold off buying the single issues, at least through the rest of this year. He's involved in a storyline called "R.I.P.", and isn't in very good shape. Combined with the fact that Neil Gaiman (the mind behind the terrific 'Sandman' series of the '90s) has been hired to write a two-part story called "Whatever Happened to the Caped Crusader" for early '09, there's a feeling that the Batman world is due for a major shake-up, if not a reboot entirely.

(In the '80s, DC realized its continuity, and multiple universes, was a headache, so it cleaned house with the 'Crisis on Infinite Earths' maxiseries, which then lead to brand-new continuities and histories for its heroes. "Whatever Happened to the Man of Tomorrow" was the name of the Superman story -- written by Alan Moore -- that served as a sort-of farewell to all the previous years before the relaunch.)

Since you don't appear opposed to trade paperbacks (and hopefully not to the slightly more expensive hardcovers), you should give Frank Miller's "All-Star Batman & Robin" a try. It's an alternate retelling of the Boy Wonder's origin, with Miller's trademark grimness in buckets. (At one point, Batman even asks Dick Grayson if he's retarded.)

Oh, and needless to say, you should read Miller's original 'The Dark Knight Returns.'

If you want more Batman, try:

Frank Miller - Batman: Year One, The Dark Knight Returns
Alan Moore - Batman: The Killing Joke
Batman: The Long Halloween

If you want to expand past Batman, there are lots of great choices:

Watchmen
Sandman (start with Vol. 1 and read them all, then read the Death graphic novels)
Marvels
Superman: Whatever Happened to the Man of Tomorrow
X-Men: Days of Future Past
Miracleman
Preacher (whole series)
Astro City (whole series)
Kingdom Come
Hellblazer (whole series)
Swamp Thing (Alan Moore years at least)
Stormwatch/Authority (the Warren Ellis volumes)

I could go on and on. Most people don't know this, but most of the Indianapolis libraries have extensive graphic novel collections. If you have a small budget, get out your library card and pick up a stack of graphic novels for free.

Also, head to your local comic shop and ask the clerk for recommendations. Those guys read everything usually.

Try Ultimates1 and Ultimates2 for a 21st Century take on Marvel's Avengers. Very cool stuff.