I just got through writing yet another book using TextMate 2 (http://shop.oreilly.com/product/0636920034261.do). It works great.
(I used my own AsciiDoc bundle; it needs a little more tweaking but it worked brilliantly too.)
m.
-- matt neuburg, phd = http://www.apeth.net/matt/ pantes anthropoi tou eidenai oregontai phusei Programming iOS 7! http://shop.oreilly.com/product/0636920031017.do iOS 7 Fundamentals! http://shop.oreilly.com/product/0636920032465.do RubyFrontier! http://www.apeth.com/RubyFrontierDocs/default.html