I recently bought Extreme Brewing by Sam Calagione, owner of Dogfish Head brewery. It's not the most exhaustive book on the subject of brewing, nor does it contain many recipes (only 25 in all, in fact). But what it lacks in quantity it makes up for in quality and sheer extravagance.
Many of the recipes use non-standard sugar sources to boost the ABV (e.g. raisins, kiwi fruit, blood oranges, chinese rock sugar etc.) and an interesting range of spices and fragrant oak chips. Best of all, it includes an extract version of Dogfish Head's famous 60 Minute IPA, which I'm brewing at the moment.
If you get the urge to try some over-the-top beers, this is a good place to start.