I had a similar idea and wanted to post my thoughts.
First, I'm pretty sure there's an official Sith-tome style book on its way. They've announced a sequel to the Jedi Path book (which is what you're talking about here, but the Jedi version) and have hinted it will be Sith themed.
Second, I don't think you should make all of it in english with a Sith font.
What is the HISTORY of this book? Has it been recovered by Jedi, reviewed by Sith, kept in Palpatine's vault...?
So many Sith were fallen Jedi. Jedi used a language called High Galactic, which is modern English, in a lot of their texts. It's an old, formal language like Latin would be to us. A good portion of the text can be written by fallen Jedi and would use High Galactic.
You can also have several passages that use images instead of words. This may be used for parts that are still unclear to us, like Force Ghosts (which GL say are light-side exclusive, BTW). Maybe some text in Sith and several cryptic images of ghosts or rituals.
You can also have additional notes left by other Sith in High Galactic. You can have page after page of Sith text, then several notes in margians or on other papers in High Galactic that point out key ideas or paraphrase important passages.
Also, about the design of the book. If you look at the official Sith we see in the movies, they aren't all uber-viscous, foaming-at-the-mouth evil. Even Darth Maul, with his devilish appearance, is very well spoken and elegant.
Look at Palpatine and Dooku's lightsabers. Or Palpatine's office and throne room, or even his robes. They're evil, sure, but they had class. In terms of appearance you can associate them with Nazi's.
- Yo Sith, I'm real happy fo' you and Imma let you finish, but Nazi officers had the best uniforms of all time! OF ALL TIME! -
The Sith in the EU are dirty and grimy and covered in animal bones and wear spiked bikini's or GWAR costumes. I think so many of them really miss the mark.
I would make the book very beautiful to look at. Very well put together, professionally done with elaborate designs all over it. Something more like a Medieval Bible than a ratty old book.