Shakespeare wrote four Great Tragedies. Two of them are very widely performed and known in the popular culture: Hamlet and Macbeth. A third, Othello, isn't quite as widespread, and carries a particular set of baggage, but still gets quite a bit more exposure than the average Shakespeare play. The final one, King Lear, falls far behind the others. It gets performed, to be sure, but it doesn't get anywhere near the number of, say, Hollywood adaptations as Hamlet and Macbeth have.
There's a good reason for that: Lear is an incredibly bleak play. Of course, we all expect bleakness from the Great Tragedies, but there's a particular viciousness and sadism in Lear that limits its appeal in this age of uplifting endings.
All the more reason for "Fool"! I haven't read any of Christopher Moore's other books, but this is one great novel, and he pulls off the incredibly challenging job of writing a comic novel adaptation of Lear. It isn't pure comedy - you can't keep Gloucester's torture in a totally happy book - but it is biting, and witty, and overall is surprisingly enjoyable.
Fool is narrated by the hero, who in this telling is Lear's Fool. Fools are in many of the Bard's plays, but Lear's Fool is probably the most well-known and sympathetic. When people talk about how Jon Stewart and Stephen Colbert are modern-day jesters who speaks truth to power, they're thinking about this character's archetype. The Fool is the only person who really sees what's happening, and who can warn the King about his mistakes without being punished for it.
There are a LOT of differences between the play and the novel, and one of the biggest is that here the Fool isn't just a commentator, but an actual actor in the play's events. He is downright Machiavellian, a far better schemer than Regan or Edmund, and his actions set mind-bogglingly-large events into motion. He's also granted a backstory and a personal journey of sorts, fleshing him out to a three-dimensional character instead of an archetype.
I really dig making the Fool a schemer. I'm a bit more ambivalent on the backstory. It's cool, and it works, but... I dunno. I can't claim that it isn't epic, but it isn't timeless in the way that Lear itself is. It's more like a really clever plot that hangs together well but doesn't illuminate anything outside itself. Which is totally fine - this is a comic novel, after all, and I wouldn't expect to receive eternal truths from it.
Oh, and the wordplay! Amazing! Virtually all the dialog is in modern English, although I suspect that some of the lines are lifted or adapted from the play's text. It's every bit as bawdy as the Bard, but using modern R-rated language instead of archaic swearing from Elizabethan England. I suspect that our reaction to this language is closer to the original audience's reaction to the original words. It's funny and shocking and clever. Moore is at his very best when the Fool is verbally bantering with someone. Actually, "Banter" isn't the right word, since the Fool totally dominates such exchanges; only Cordelia and Regan can come close to matching his wits.
There's a cool afterword to the book in which Moore talks about writing it. It's fascinating to get insight into making a book like this. He points out that the timeline of the original play is really hard to pin down; the historic King Leir probably lived around 600 BC, long before any of the cities in the play (Gloucester, Kent, etc.) were founded; there's a weird mixture of Roman and Celtic and Christian components to the tale. At one point in the original play, Moore writes, Shakespeare himself acknowledges how screwed up the timeline is when a character says something like, "This is the prophecy written by Merlin, even though he will be born after I die." It's as though Shakespeare is throwing up his hands and saying, "I don't know when the play is set, either! Wheeee!" Moore took that as his license to do what he wanted to, and he keeps the same sort of mixed-up timeline as the original without worrying about whether it makes sense. This almost entirely works, except for one really bizarre two-page digression on the two popes - rather than the historic Pope and Antipope, this is a conflict between the Discount Pope and the Retail Pope. It's pretty confusing, and while I like the idea of dueling Popes, it has nothing in the slightest to do with anything else and totally breaks the rhythm of the chapter. That's an anomaly, though... for the most part, Moore takes license with the timeframe in the service of doing other interesting stuff or establishing atmosphere.
This is the first book of Moore's that I've read, and it sounds like it might be pretty different from his other stuff.... I'm sure I'll check out something else from him at some point, though I'm not in an enormous rush to do so. In the meantime, blow, wind! Rage, rain! Get-Ready! The World is Coming to an End!