Well,
As far as I know you cannot directly make your own updates to the eFlyBook because of the OEM software installed.
HOWEVER, for less than the cost of an eFlyBook, you can buy a iLead from
iRex (in Germany), which is the exact hardware the eFlyBook is based on. You can then load the
digital-Terminal Procedures Publications (dTPP) PDF file. I have both a first and second generation iRex, and love them both very much.
In addition to providing you with dTPP, the regular iRex also provides e-book reading, including the mobipocket secured e-books, which includes most new commercial releases.
You could also go with something like the
jinke Hanlin V2 or V3 (I have the V3 and really like it) reader. On the downside its a little smaller than the iLead, but a LOT less expensive.
Unfortunately, there is currently no software (of which I am aware) to automagically update the TPPs each month. I would like to write some (in my spare time -- actually now that Oshkosh is happening, I may have a little spare time). I have not written it so far, however, as last time I asked around it seemed like there was little or no interest in a little program to automatically dump plates to an iLead/V3/Sony Reader etc.
In any case, I do love using eInk for plates, and expect to see more of it in the future.