Genius was built to help those who need to search in immense txt files, and who need some sophisticated tool to search among many books or documents.
As you may know or you need to know, regular expression is horribly helpful for text searching, and thats exactly the main character of Genius search. You can copy your library into Genius via iTunes, and explore the ocean of text freely.
Currently only .txt files of any encoding and 4-level directory specifying are supported, more are coming.
Special search grammar: searching ///abc/def/.{0,10}/// will get the results for searching .{0,10}abcdef and abc.{0,10}def and abcdef.{0,10} and .{0,10}defabc and def.{0,10}abc and defabc.{0,10}. et cetera.