Can't get code book of Fighter's guild quest. The girl from South Club says that F.Guild works on Camonna Tong, so Thieves Guild needs this book, and that decision is mine. When I tries to steal the book, there is no book in her inv. How to get this book? Please help!

You have joined both the Fighters and Thieves guilds, right?
If you are in the Thieves guild, you are not allowed to be a traitor by Sottilde and help the Fighters Guild so you have a couple of options to use depending on were your loyalties lie.

SPOILERS/CHEATS
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1. Pick-pocket , but it is not working for you...
2. Kill, get kicked out of Thieves Guild
3. Taunt until she attacks and then kill (may take a couple of reloads because sometimes the game "credits" you with a criminal action)
4. a. Press ~
b. In console window, type
player->AddItem "bk_sottildescodebook", 1
c. Press ~
5. Reload before you joined the Thieves Guild
6. Give up the Fighters Guild

Good luck!

Your pickpocketing skills must be up there, so if they're not, get them up and come back to this quest. You must get her disposition up for the book to be in her inventory when you pickpocket. If you stand on the side by the table, (she is facing the door), use invisibility and sneak and then pickpocket. This should work.

Even if the pickpocket fails, you only have to contend with an enraged Sottilde, not the rest of the guild. But you still get booted out of the guild.

Save and just keep reloading until you get it right. If you pickpocket, she never even realizes her book is gone.

Thanks a lot for your help. Finally, I stole the book.