I have the same problem, can someone confirm that it is possible to edit the author of a book. I choose "save as" and save it as Ismon.dat then chose replace.
edit: i realized i opened the wrong file... I now opens the level.dat change the author in the book. Then i press save (also tested saves as directly) the i press save as and save it as level2.dat
Then i test to open the level2.dat and can se that the author have been changed. Then i remove the old level.dat and rename the level2.dat to level.dat, i test to open the level.dat once more and the author is still changed. But when i start minecraft the author name have been changed back again...
I managed to change the author once when i tested and thought it worked but i can't get it work anymore, any help are very appreciated.
You have to save it as level.dat and replace the old one.
Every single time I click on the download link, I gives me a Error message from the website, can't you just use MediaFire or something? That would really help, do it as a Mirror Download or something. Thanks.