He likes palindromes, sentences that are the same forward and backward. Things like : "Are we not drawn onward, we few, drawn onward to new era?"
He wrote a version of The Raven which is a mnemonic for Pi -- each word, in turn, has a number of letters corresponding to the next digit of Pi. You'll also notice that it keeps rhyme and meter, including internal line rhymes. There's a longer version he does which goes through several consecutive poems, continuing Pi from the digit at the end of the previous poem. Scary? You bet.
It gets worse. He's the author of The Anagrammed Bible. It's good enough that I went ahead and bought a dead-tree copy. Check out some of those Bible verses, and the basically-equivalent rephrases he anagrammed them into. He's really good.
Of course, he's also done some more impressive stuff yet, like translating a chunk of Dante's Inferno from Italian into English while keeping it an anagram -- and it's good (scroll down to find it). Or his anagram of a Shakespeare sonnet, which is also a sonnet with the same rhyme and meter.
Some of it's awe-inspiring, a little of it's not great, and almost all of it is jaw-dropping. Check him out.