Over the years, the Hulk's many personalities and incarnations have left him with more alternate universe counterparts and distinct eras than any Marvel property that isn't around having an X-gene. This two-issue miniseries seeks to investigate some of those interpretations a little more, for no other reason than the fun of it.
Strangely, by exploring some of these stories and universes, "Hulk: Broken Worlds" offers an unlikely antidote for those who aren't finding Loeb's take on the character to their tastes. Steeped in the Hulk's history, these tales are bound to click with exactly the audience put off by the current back-to-basics approach.
Readers, then, can expect to find a story about Hulk and Jarella in the Microverse (by the classic team of Roy Thomas and Herb Trimpe), a tale from the recent House of M universe (by Fred Van Lente), a Hulk 2099 story (with some astonishingly Sienkiewicz-esque artwork) and the crown jewel (of this issue at least) a Peter David-penned "Future Imperfect" vignette, featuring Rodney Buchemi doing his best George Perez. All the stories are entertaining in their own right, but if there's any justice in the world, the Future Imperfect one will be collected alongside its parent series in the future, purely for completeness' sake.
That aside, your enjoyment of the other shorts will probably be based on how fondly you remember the original runs. The Hulk/Jarella piece is from a well-loved run of stories, and finds itself oddly relevant again in light of the current "Hulk" arc. The Hulk 2099 story. . . is less so. The House of M reality is itself still recent enough to feel familiar, but that version of the Hulk, totally peripheral to the 2004 crossover, may not be well-known enough to hold any interest if you didn't read the original arc.
There's nothing technically wrong with any of the stories, even if you approach them purely as "What If?" shorts -- they do stand alone, but let's not pretend that the comic is anything more than an exercise in servicing nostalgia. That's not necessarily a bad thing, but it does mean the book isn't ever going to be on any "top 10 comics in 2009" lists. It's one for hardcore Hulk enthusiasts only, but at least they will enjoy it.